Merge branch 'main' into issue/mitgliederverwaltung-420

Integrate current main (CSV import, GDPR join-form description, dependency and
tooling bumps) into the bulk-actions-dropdown feature. Gettext catalogs were
reconciled with mix gettext.extract --merge; the CHANGELOG Unreleased entries
of both sides were combined.

lib/membership/custom_field.ex

@@ -12,6 +12,8 @@ defmodule Mv.Membership.CustomField do
   - `slug` - URL-friendly, immutable identifier automatically generated from name (e.g., "phone-mobile")
   - `value_type` - Data type constraint (`:string`, `:integer`, `:boolean`, `:date`, `:email`). Immutable after creation.
   - `description` - Optional human-readable description
+  - `join_description` - Optional label shown for this field on the public join form
+    (e.g., a GDPR confirmation text); supports inline external links. Falls back to `name` when nil.
   - `required` - If true, all members must have this custom field (future feature)
   - `show_in_overview` - If true, this custom field will be displayed in the member overview table and can be sorted
 
@@ -61,7 +63,14 @@ defmodule Mv.Membership.CustomField do
   end
 
   actions do
-    default_accept [:name, :value_type, :description, :required, :show_in_overview]
+    default_accept [
+      :name,
+      :value_type,
+      :description,
+      :join_description,
+      :required,
+      :show_in_overview
+    ]
 
     read :read do
       primary? true
@@ -69,13 +78,13 @@ defmodule Mv.Membership.CustomField do
     end
 
     create :create do
-      accept [:name, :value_type, :description, :required, :show_in_overview]
+      accept [:name, :value_type, :description, :join_description, :required, :show_in_overview]
       change Mv.Membership.Changes.GenerateSlug
       validate string_length(:slug, min: 1)
     end
 
     update :update do
-      accept [:name, :description, :required, :show_in_overview]
+      accept [:name, :description, :join_description, :required, :show_in_overview]
       require_atomic? false
 
       validate fn changeset, _context ->
@@ -139,6 +148,15 @@ defmodule Mv.Membership.CustomField do
         trim?: true
       ]
 
+    attribute :join_description, :string,
+      allow_nil?: true,
+      public?: true,
+      description: "Label shown for this field on the public join form; supports external links",
+      constraints: [
+        max_length: 1000,
+        trim?: true
+      ]
+
     attribute :required, :boolean,
       default: false,
       allow_nil?: false

lib/mv/membership/custom_field_value_formatter.ex

@@ -4,13 +4,13 @@ defmodule Mv.Membership.CustomFieldValueFormatter do
 
   Same logic as the member overview Formatter but without Gettext or web helpers,
   so it can be used from the Membership context. For boolean: "Yes"/"No";
-  for date: European format (dd.mm.yyyy).
+  for date: ISO-8601 (YYYY-MM-DD) so exported values can be re-imported.
   """
   @doc """
   Formats a custom field value for plain text (e.g. CSV).
 
   Handles nil, Ash.Union, JSONB map, and direct values. Uses custom_field.value_type
-  for typing. Boolean -> "Yes"/"No", Date -> dd.mm.yyyy.
+  for typing. Boolean -> "Yes"/"No", Date -> ISO-8601 (YYYY-MM-DD).
   """
   def format_custom_field_value(nil, _custom_field), do: ""
 
@@ -18,6 +18,10 @@ defmodule Mv.Membership.CustomFieldValueFormatter do
     format_value_by_type(value, type, custom_field)
   end
 
+  def format_custom_field_value(%Date{} = value, custom_field) do
+    format_value_by_type(value, :date, custom_field)
+  end
+
   def format_custom_field_value(value, custom_field) when is_map(value) do
     type = Map.get(value, "type") || Map.get(value, "_union_type")
     val = Map.get(value, "value") || Map.get(value, "_union_value")
@@ -41,12 +45,12 @@ defmodule Mv.Membership.CustomFieldValueFormatter do
   defp format_value_by_type(value, :boolean, _), do: to_string(value)
 
   defp format_value_by_type(%Date{} = date, :date, _) do
-    Calendar.strftime(date, "%d.%m.%Y")
+    Date.to_iso8601(date)
   end
 
   defp format_value_by_type(value, :date, _) when is_binary(value) do
     case Date.from_iso8601(value) do
-      {:ok, date} -> Calendar.strftime(date, "%d.%m.%Y")
+      {:ok, date} -> Date.to_iso8601(date)
       _ -> value
     end
   end

lib/mv/membership/import/column_resolver.ex

@@ -0,0 +1,258 @@
+defmodule Mv.Membership.Import.ColumnResolver do
+  @moduledoc """
+  Read-only resolution of CSV import columns against the database.
+
+  Given the `HeaderMapper.build_maps/2` result, the raw numbered rows, and an
+  actor, `resolve/3` determines:
+
+  - which group names in the groups column already exist (`groups_found`) and
+    which would have to be created (`groups_to_create`);
+  - a small set of preview rows for the mapping preview UI.
+
+  No database writes happen here; the resolver only reads. Group creation and
+  member-group assignment happen during processing via `create_or_find_group/3`.
+
+  This module has no Phoenix or web dependencies.
+  """
+
+  require Logger
+
+  alias Mv.Membership.Import.HeaderMapper
+
+  @preview_row_limit 3
+
+  @type numbered_row :: {pos_integer(), [String.t()]}
+
+  @type resolution :: %{
+          groups_found: [%{id: String.t(), name: String.t()}],
+          groups_to_create: [String.t()],
+          fee_type_map: %{String.t() => String.t()},
+          fee_type_warnings: [String.t()],
+          has_empty_fee_type_cells?: boolean(),
+          preview_rows: [[String.t()]]
+        }
+
+  @doc """
+  Resolves the group and fee-type columns of an import against the database and
+  extracts preview rows.
+
+  Returns a map with `:groups_found`, `:groups_to_create`, `:fee_type_map`,
+  `:fee_type_warnings`, `:has_empty_fee_type_cells?`, and `:preview_rows`.
+  """
+  @spec resolve(map(), [numbered_row()], term()) :: resolution()
+  def resolve(header_maps, rows, actor) do
+    %{
+      groups_found: groups_found,
+      groups_to_create: groups_to_create
+    } = resolve_groups(header_maps, rows, actor)
+
+    %{
+      fee_type_map: fee_type_map,
+      fee_type_warnings: fee_type_warnings,
+      has_empty_fee_type_cells?: has_empty_fee_type_cells?
+    } = resolve_fee_types(header_maps, rows, actor)
+
+    %{
+      groups_found: groups_found,
+      groups_to_create: groups_to_create,
+      fee_type_map: fee_type_map,
+      fee_type_warnings: fee_type_warnings,
+      has_empty_fee_type_cells?: has_empty_fee_type_cells?,
+      preview_rows: preview_rows(rows)
+    }
+  end
+
+  defp resolve_groups(%{groups_column_index: nil}, _rows, _actor) do
+    %{groups_found: [], groups_to_create: []}
+  end
+
+  defp resolve_groups(%{groups_column_index: index}, rows, actor) do
+    existing_groups = list_groups(actor)
+    lookup = build_group_lookup(existing_groups)
+
+    names = unique_group_names(rows, index)
+
+    {found, to_create} =
+      Enum.reduce(names, {[], []}, fn name, {found, to_create} ->
+        case Map.get(lookup, normalize_name(name)) do
+          nil -> {found, [name | to_create]}
+          group -> {[%{id: group.id, name: group.name} | found], to_create}
+        end
+      end)
+
+    %{groups_found: Enum.reverse(found), groups_to_create: Enum.reverse(to_create)}
+  end
+
+  defp resolve_fee_types(%{fee_type_column_index: nil}, _rows, _actor) do
+    %{fee_type_map: %{}, fee_type_warnings: [], has_empty_fee_type_cells?: false}
+  end
+
+  defp resolve_fee_types(%{fee_type_column_index: index}, rows, actor) do
+    lookup = build_fee_type_lookup(actor)
+
+    cells = Enum.map(rows, fn {_line, values} -> Enum.at(values, index) end)
+
+    has_empty? = Enum.any?(cells, &blank?/1)
+
+    {fee_type_map, warnings} =
+      cells
+      |> Enum.reject(&blank?/1)
+      |> Enum.uniq_by(&normalize_fee_type_name/1)
+      |> Enum.reduce({%{}, []}, fn name, {map, warnings} ->
+        case Map.get(lookup, normalize_fee_type_name(name)) do
+          nil -> {map, [String.trim(name) | warnings]}
+          id -> {Map.put(map, normalize_fee_type_name(name), id), warnings}
+        end
+      end)
+
+    %{
+      fee_type_map: fee_type_map,
+      fee_type_warnings: Enum.reverse(warnings),
+      has_empty_fee_type_cells?: has_empty?
+    }
+  end
+
+  @doc """
+  Normalizes a fee-type name using the same rules as CSV header normalization
+  (trim, lowercase, transliterate, drop hyphens and whitespace).
+  """
+  @spec normalize_fee_type_name(String.t() | nil) :: String.t()
+  def normalize_fee_type_name(name) when is_binary(name), do: HeaderMapper.normalize_header(name)
+  def normalize_fee_type_name(_), do: ""
+
+  defp build_fee_type_lookup(actor) do
+    actor
+    |> list_fee_types()
+    |> Enum.reduce(%{}, fn fee_type, acc ->
+      normalized = normalize_fee_type_name(fee_type.name)
+
+      if Map.has_key?(acc, normalized) do
+        Logger.warning(
+          "Multiple membership fee types normalize to #{inspect(normalized)}; using the first match for CSV import."
+        )
+
+        acc
+      else
+        Map.put(acc, normalized, fee_type.id)
+      end
+    end)
+  end
+
+  defp list_fee_types(actor) do
+    Mv.MembershipFees.list_membership_fee_types!(actor: actor)
+  end
+
+  defp blank?(nil), do: true
+  defp blank?(value) when is_binary(value), do: String.trim(value) == ""
+  defp blank?(_), do: false
+
+  @doc """
+  Finds an existing group by name (case-insensitive) or creates it.
+
+  Looks first in the pre-fetched `groups` list, then in the database (to catch
+  groups created earlier in the same import), and only creates a new group when
+  none is found. This keeps group resolution idempotent across re-imports.
+  """
+  @spec create_or_find_group(String.t(), [Mv.Membership.Group.t()], term()) ::
+          {:ok, Mv.Membership.Group.t()} | {:error, term()}
+  def create_or_find_group(name, groups, actor) when is_binary(name) do
+    trimmed = String.trim(name)
+    normalized = normalize_name(trimmed)
+
+    case find_group_in_list(groups, normalized) do
+      nil -> find_or_create_group(trimmed, normalized, actor)
+      group -> {:ok, group}
+    end
+  end
+
+  defp find_group_in_list(groups, normalized) do
+    Enum.find(groups, fn group -> normalize_name(group.name) == normalized end)
+  end
+
+  defp find_or_create_group(trimmed, normalized, actor) do
+    case fetch_group_by_normalized_name(normalized, actor) do
+      nil -> create_group(trimmed, normalized, actor)
+      group -> {:ok, group}
+    end
+  end
+
+  # Normalizes the Ash code-interface return to a two-shape result.
+  #
+  # On a create failure the group may have been created concurrently by another
+  # import session between our read and our write (the DB unique index is the
+  # final arbiter, and the name validation is fail-open). Re-fetch by normalized
+  # name and link to the existing group rather than failing the row.
+  defp create_group(name, normalized, actor) do
+    case Mv.Membership.create_group(%{name: name}, actor: actor) do
+      {:ok, %Mv.Membership.Group{} = group} ->
+        {:ok, group}
+
+      {:error, reason} ->
+        case fetch_group_by_normalized_name(normalized, actor) do
+          nil -> {:error, reason}
+          group -> {:ok, group}
+        end
+    end
+  end
+
+  # Fetches a single group by case-insensitive name using a name-filtered query
+  # rather than reading the whole groups table. `normalized` is the trimmed,
+  # lower-cased name; the DB comparison uses LOWER(name) consistent with the
+  # Group resource's case-insensitive uniqueness constraint.
+  defp fetch_group_by_normalized_name(normalized, actor) do
+    require Ash.Query
+
+    Mv.Membership.Group
+    |> Ash.Query.filter(fragment("LOWER(?) = ?", name, ^normalized))
+    |> Ash.read(actor: actor, domain: Mv.Membership)
+    |> case do
+      {:ok, [group | _]} -> group
+      _ -> nil
+    end
+  end
+
+  @doc """
+  Splits a raw groups-cell value into trimmed, non-empty group names.
+  """
+  @spec split_group_names(String.t() | nil) :: [String.t()]
+  def split_group_names(nil), do: []
+
+  def split_group_names(cell) when is_binary(cell) do
+    cell
+    |> String.split(",")
+    |> Enum.map(&String.trim/1)
+    |> Enum.reject(&(&1 == ""))
+  end
+
+  defp unique_group_names(rows, index) do
+    rows
+    |> Enum.flat_map(fn {_line, values} ->
+      values
+      |> Enum.at(index)
+      |> split_group_names()
+    end)
+    |> Enum.uniq_by(&normalize_name/1)
+  end
+
+  defp preview_rows(rows) do
+    rows
+    |> Enum.take(@preview_row_limit)
+    |> Enum.map(fn {_line, values} -> values end)
+  end
+
+  defp list_groups(actor) do
+    Mv.Membership.list_groups!(actor: actor)
+  end
+
+  defp build_group_lookup(groups) do
+    Enum.reduce(groups, %{}, fn group, acc ->
+      Map.put(acc, normalize_name(group.name), group)
+    end)
+  end
+
+  # Case-insensitive comparison consistent with the Group resource's
+  # case-insensitive name uniqueness.
+  defp normalize_name(name) when is_binary(name) do
+    name |> String.trim() |> String.downcase()
+  end
+end

lib/mv/membership/import/header_mapper.ex

@@ -29,12 +29,21 @@ defmodule Mv.Membership.Import.HeaderMapper do
 
   Supports English and German header variants (e.g. "Email" / "E-Mail", "Join Date" / "Beitrittsdatum").
 
+  ## Special columns
+
+  - **groups** – Many-to-many relationship (through member_groups). Recognized via the
+    `groups_column_index` key (headers `Groups`, `Gruppen`, `Gruppe`). Comma-separated
+    names are resolved during processing; missing groups are auto-created.
+  - **membership_fee_type** – Recognized via the `fee_type_column_index` key (headers
+    `Fee Type`, `fee_type`, `membership_fee_type`, `Beitragsart`). Names are matched to
+    existing fee types; unknown names fall back to the default fee type.
+
   ## Fields not supported for import
 
   - **membership_fee_status** – Computed (calculation from membership fee cycles). Not stored;
-    cannot be set via CSV. Export can include it.
-  - **groups** – Many-to-many relationship (through member_groups). Import would require
-    resolving group names/slugs to IDs and creating associations; not in current import scope.
+    cannot be set via CSV. Export can include it. Fee-status header variants
+    (`Membership Fee Status`, `Bezahlstatus`, `Mitgliedsbeitragsstatus`) are explicitly
+    placed in the `ignored` list and never mapped.
 
   ## Custom Field Detection
 
@@ -47,10 +56,10 @@ defmodule Mv.Membership.Import.HeaderMapper do
       "e-mail"
 
       iex> HeaderMapper.build_maps(["Email", "First Name"], [])
-      {:ok, %{member: %{email: 0, first_name: 1}, custom: %{}, unknown: []}}
+      {:ok, %{member: %{email: 0, first_name: 1}, custom: %{}, unknown: [], ignored: [], groups_column_index: nil, fee_type_column_index: nil}}
 
       iex> HeaderMapper.build_maps(["Email", "CustomField"], [%{id: "cf1", name: "CustomField"}])
-      {:ok, %{member: %{email: 0}, custom: %{"cf1" => 1}, unknown: []}}
+      {:ok, %{member: %{email: 0}, custom: %{"cf1" => 1}, unknown: [], ignored: [], groups_column_index: nil, fee_type_column_index: nil}}
   """
 
   @type column_map :: %{atom() => non_neg_integer()}
@@ -60,6 +69,33 @@ defmodule Mv.Membership.Import.HeaderMapper do
   # Required member fields
   @required_member_fields [:email]
 
+  # Fee-status header variants that must never be imported (computed/read-only field).
+  # Stored already-normalized; checked before member, custom, groups, and fee-type mapping.
+  # Maintain this list when new locale translations for fee-status are added.
+  @ignored_normalized [
+    "membershipfeestatus",
+    "mitgliedsbeitragsstatus",
+    "bezahlstatus",
+    # DE export label for membership_fee_start_date — system-managed, not importable
+    "startdatummitgliedsbeitrag"
+  ]
+
+  # Normalized header variants for the groups column. The column is resolved to
+  # group associations during import; it is never a member or custom field.
+  @groups_column_normalized [
+    "groups",
+    "gruppen",
+    "gruppe"
+  ]
+
+  # Normalized header variants for the membership fee-type column. The column is
+  # resolved to a MembershipFeeType during import; it is never a member or custom field.
+  @fee_type_column_normalized [
+    "membershipfeetype",
+    "feetype",
+    "beitragsart"
+  ]
+
   # Canonical member fields with their raw variants
   # These will be normalized at runtime when building the lookup map
   @member_field_variants_raw %{
@@ -239,30 +275,79 @@ defmodule Mv.Membership.Import.HeaderMapper do
 
   ## Returns
 
-  - `{:ok, %{member: column_map, custom: custom_field_map, unknown: unknown_headers}}` on success
+  - `{:ok, %{member: column_map, custom: custom_field_map, unknown: unknown_headers,
+    ignored: [non_neg_integer], groups_column_index: non_neg_integer | nil,
+    fee_type_column_index: non_neg_integer | nil}}` on success
   - `{:error, reason}` on error (missing required field, duplicate headers)
 
+  The `ignored` list holds the indices of fee-status columns (computed/read-only),
+  which are never mapped to member or custom fields.
+
   ## Examples
 
       iex> build_maps(["Email", "First Name"], [])
-      {:ok, %{member: %{email: 0, first_name: 1}, custom: %{}, unknown: []}}
+      {:ok, %{member: %{email: 0, first_name: 1}, custom: %{}, unknown: [], ignored: [], groups_column_index: nil, fee_type_column_index: nil}}
 
       iex> build_maps(["Email", "CustomField"], [%{id: "cf1", name: "CustomField"}])
-      {:ok, %{member: %{email: 0}, custom: %{"cf1" => 1}, unknown: []}}
+      {:ok, %{member: %{email: 0}, custom: %{"cf1" => 1}, unknown: [], ignored: [], groups_column_index: nil, fee_type_column_index: nil}}
 
   """
   @spec build_maps([String.t()], [map()]) ::
-          {:ok, %{member: column_map(), custom: custom_field_map(), unknown: unknown_headers()}}
+          {:ok,
+           %{
+             member: column_map(),
+             custom: custom_field_map(),
+             unknown: unknown_headers(),
+             ignored: [non_neg_integer()],
+             groups_column_index: non_neg_integer() | nil,
+             fee_type_column_index: non_neg_integer() | nil
+           }}
           | {:error, String.t()}
   def build_maps(headers, custom_fields) when is_list(headers) and is_list(custom_fields) do
-    with {:ok, member_map, unknown_after_member} <- build_member_map(headers),
+    ignored = ignored_indices(headers)
+    groups_column_index = first_matching_index(headers, @groups_column_normalized)
+    fee_type_column_index = first_matching_index(headers, @fee_type_column_normalized)
+
+    reserved =
+      [groups_column_index, fee_type_column_index | ignored]
+      |> Enum.reject(&is_nil/1)
+      |> MapSet.new()
+
+    with {:ok, member_map, unknown_after_member} <- build_member_map(headers, reserved),
          {:ok, custom_map, unknown_after_custom} <-
            build_custom_field_map(headers, unknown_after_member, custom_fields, member_map) do
       unknown = Enum.map(unknown_after_custom, &Enum.at(headers, &1))
-      {:ok, %{member: member_map, custom: custom_map, unknown: unknown}}
+
+      {:ok,
+       %{
+         member: member_map,
+         custom: custom_map,
+         unknown: unknown,
+         ignored: ignored,
+         groups_column_index: groups_column_index,
+         fee_type_column_index: fee_type_column_index
+       }}
     end
   end
 
+  # Returns the index of the first header whose normalized form is in `variants`,
+  # or nil if none match.
+  defp first_matching_index(headers, variants) do
+    headers
+    |> Enum.with_index()
+    |> Enum.find_value(fn {header, index} ->
+      if normalize_header(header) in variants, do: index
+    end)
+  end
+
+  # Returns the column indices whose normalized header is in the fee-status ignore list.
+  defp ignored_indices(headers) do
+    headers
+    |> Enum.with_index()
+    |> Enum.filter(fn {header, _index} -> normalize_header(header) in @ignored_normalized end)
+    |> Enum.map(fn {_header, index} -> index end)
+  end
+
   # --- Private Functions ---
 
   # Transliterates German umlauts and special characters
@@ -304,13 +389,14 @@ defmodule Mv.Membership.Import.HeaderMapper do
     |> String.replace(" ", "")
   end
 
-  # Builds member field column map
-  defp build_member_map(headers) do
+  # Builds member field column map, skipping reserved (e.g. ignored) indices.
+  defp build_member_map(headers, reserved) do
     result =
       headers
       |> Enum.with_index()
       |> Enum.reduce_while({%{}, []}, fn {header, index}, {acc_map, acc_unknown} ->
-        normalized = normalize_header(header)
+        normalized =
+          if MapSet.member?(reserved, index), do: "", else: normalize_header(header)
 
         case process_member_header(header, index, normalized, acc_map, %{}) do
           {:error, reason} ->

lib/mv/membership/import/import_runner.ex

@@ -80,7 +80,7 @@ defmodule Mv.Membership.Import.ImportRunner do
     all_errors = progress.errors ++ chunk_result.errors
     new_errors = Enum.take(all_errors, max_errors)
     errors_truncated? = length(all_errors) > max_errors
-    new_warnings = progress.warnings ++ Map.get(chunk_result, :warnings, [])
+    new_warnings = Enum.uniq(progress.warnings ++ Map.get(chunk_result, :warnings, []))
 
     chunks_processed = current_chunk_idx + 1
     new_status = if chunks_processed >= progress.total_chunks, do: :done, else: :running
@@ -97,6 +97,20 @@ defmodule Mv.Membership.Import.ImportRunner do
     }
   end
 
+  @doc """
+  Carries the in-memory group snapshot grown by a chunk back into `import_state`
+  so the next chunk reuses groups created earlier instead of re-reading the
+  Group table. When the chunk result omits `groups_found`, the state is returned
+  unchanged.
+  """
+  @spec carry_groups_forward(map(), map()) :: map()
+  def carry_groups_forward(import_state, chunk_result) do
+    case Map.fetch(chunk_result, :groups_found) do
+      {:ok, groups_found} -> Map.put(import_state, :groups_found, groups_found)
+      :error -> import_state
+    end
+  end
+
   @doc """
   Returns the next action after processing a chunk: send the next chunk index or done.
   """

lib/mv/membership/import/member_csv.ex

@@ -6,7 +6,7 @@ defmodule Mv.Membership.Import.MemberCSV do
 
   This module provides the core API for CSV member import functionality:
   - `prepare/2` - Parses and validates CSV content, returns import state
-  - `process_chunk/3` - Processes a chunk of rows and creates members
+  - `process_chunk/4` - Processes a chunk of rows and creates members
 
   ## Error Handling
 
@@ -22,13 +22,24 @@ defmodule Mv.Membership.Import.MemberCSV do
   - `column_map` - Map of canonical field names to column indices
   - `custom_field_map` - Map of custom field names to column indices
   - `warnings` - List of warning messages (e.g., unknown custom field columns)
+  - `headers` - The raw CSV header row
+  - `ignored` - Header names of ignored (fee-status) columns
+  - `groups_column_index` / `fee_type_column_index` - Indices for resolved columns (or nil)
+  - `groups_found` / `groups_to_create` - Existing and to-be-created groups from the preview
+  - `fee_type_map` - Normalized fee-type name to id, for matched fee types
+  - `fee_type_warnings` - Unmatched fee-type names surfaced in the preview
+  - `has_empty_fee_type_cells?` - Whether any fee-type cell is blank (default applies)
+  - `preview_rows` - Up to 3 sample data rows for the mapping preview
 
   ## Chunk Results
 
-  The `chunk_result` returned by `process_chunk/3` contains:
+  The `chunk_result` returned by `process_chunk/4` contains:
   - `inserted` - Number of successfully created members
   - `failed` - Number of failed member creations
   - `errors` - List of `%MemberCSV.Error{}` structs (capped at 50 per import)
+  - `groups_found` - The in-memory group snapshot grown while processing this
+    chunk; thread it into the next chunk's `:groups_found` opt so groups created
+    in an earlier chunk are reused without re-reading the Group table
 
   ## Examples
 
@@ -37,7 +48,9 @@ defmodule Mv.Membership.Import.MemberCSV do
 
       # Process first chunk
       chunk = Enum.at(import_state.chunks, 0)
-      {:ok, result} = MemberCSV.process_chunk(chunk, import_state.column_map)
+
+      {:ok, result} =
+        MemberCSV.process_chunk(chunk, import_state.column_map, import_state.custom_field_map, [])
   """
 
   defmodule Error do
@@ -66,16 +79,29 @@ defmodule Mv.Membership.Import.MemberCSV do
           custom_field_lookup: %{
             String.t() => %{id: String.t(), value_type: atom(), name: String.t()}
           },
-          warnings: list(String.t())
+          warnings: list(String.t()),
+          headers: list(String.t()),
+          ignored: list(String.t()),
+          groups_column_index: non_neg_integer() | nil,
+          fee_type_column_index: non_neg_integer() | nil,
+          groups_found: list(%{id: String.t(), name: String.t()}),
+          groups_to_create: list(String.t()),
+          fee_type_map: %{String.t() => String.t()},
+          fee_type_warnings: list(String.t()),
+          has_empty_fee_type_cells?: boolean(),
+          preview_rows: list(list(String.t()))
         }
 
   @type chunk_result :: %{
           inserted: non_neg_integer(),
           failed: non_neg_integer(),
           errors: list(Error.t()),
-          errors_truncated?: boolean()
+          errors_truncated?: boolean(),
+          warnings: list(String.t()),
+          groups_found: list(Mv.Membership.Group.t() | %{id: String.t(), name: String.t()})
         }
 
+  alias Mv.Membership.Import.ColumnResolver
   alias Mv.Membership.Import.CsvParser
   alias Mv.Membership.Import.HeaderMapper
 
@@ -139,13 +165,27 @@ defmodule Mv.Membership.Import.MemberCSV do
       # Build custom field lookup for efficient value processing
       custom_field_lookup = build_custom_field_lookup(custom_fields)
 
+      # Resolve DB-backed columns (groups, fee types) read-only for the preview.
+      resolution = ColumnResolver.resolve(maps, rows, actor)
+      ignored_headers = Enum.map(maps.ignored, &Enum.at(headers, &1))
+
       {:ok,
        %{
          chunks: chunks,
          column_map: maps.member,
          custom_field_map: maps.custom,
          custom_field_lookup: custom_field_lookup,
-         warnings: warnings
+         warnings: warnings,
+         headers: headers,
+         ignored: ignored_headers,
+         groups_column_index: maps.groups_column_index,
+         fee_type_column_index: maps.fee_type_column_index,
+         groups_found: resolution.groups_found,
+         groups_to_create: resolution.groups_to_create,
+         fee_type_map: resolution.fee_type_map,
+         fee_type_warnings: resolution.fee_type_warnings,
+         has_empty_fee_type_cells?: resolution.has_empty_fee_type_cells?,
+         preview_rows: resolution.preview_rows
        }}
     end
   end
@@ -180,7 +220,7 @@ defmodule Mv.Membership.Import.MemberCSV do
       end)
 
     case HeaderMapper.build_maps(headers, custom_field_maps) do
-      {:ok, %{member: member_map, custom: custom_map, unknown: unknown}} ->
+      {:ok, %{unknown: unknown} = maps} ->
         # Build warnings for unknown custom field columns
         warnings =
           unknown
@@ -197,7 +237,7 @@ defmodule Mv.Membership.Import.MemberCSV do
             )
           end)
 
-        {:ok, %{member: member_map, custom: custom_map}, warnings}
+        {:ok, maps, warnings}
 
       {:error, reason} ->
         {:error, reason}
@@ -250,9 +290,20 @@ defmodule Mv.Membership.Import.MemberCSV do
         Map.put(acc, custom_field_id, value)
       end)
 
-    %{member: member_map, custom: custom_map}
+    %{
+      member: member_map,
+      custom: custom_map,
+      fee_type: cell_at(row_tuple, tuple_size, maps.fee_type_column_index),
+      groups: cell_at(row_tuple, tuple_size, maps.groups_column_index)
+    }
   end
 
+  # Returns the raw cell at the given index, or nil if the column is absent.
+  defp cell_at(_row_tuple, _size, nil), do: nil
+
+  defp cell_at(row_tuple, size, index) when index < size, do: elem(row_tuple, index)
+  defp cell_at(_row_tuple, _size, _index), do: ""
+
   @doc """
   Processes a chunk of CSV rows and creates members.
 
@@ -268,12 +319,18 @@ defmodule Mv.Membership.Import.MemberCSV do
   - `chunk_rows_with_lines` - List of tuples `{csv_line_number, row_map}` where:
     - `csv_line_number` - Physical line number in CSV (1-based)
     - `row_map` - Map with `:member` and `:custom` keys containing field values
-  - `column_map` - Map of canonical field names (atoms) to column indices (for reference)
-  - `custom_field_map` - Map of custom field IDs (strings) to column indices (for reference)
+  - `column_map` - Unused; kept for backward-compatible call sites. Field values are
+    read from each row's pre-built `:member`/`:custom` maps, not from this argument.
+  - `custom_field_map` - Unused; kept for backward-compatible call sites (see above).
   - `opts` - Optional keyword list for processing options:
     - `:custom_field_lookup` - Map of custom field IDs to metadata (default: `%{}`)
     - `:existing_error_count` - Number of errors already collected in previous chunks (default: `0`)
     - `:max_errors` - Maximum number of errors to collect per import overall (default: `50`)
+    - `:actor` - Actor used for all writes (default: the system actor)
+    - `:fee_type_map` - Map of normalized fee-type name to fee-type id, used to resolve
+      each row's fee-type cell (default: `%{}`)
+    - `:groups_found` - List of pre-fetched `Group` structs seeding in-memory group
+      resolution; the snapshot grows as groups are auto-created (default: `[]`)
 
   ## Error Capping
 
@@ -312,27 +369,49 @@ defmodule Mv.Membership.Import.MemberCSV do
     existing_error_count = Keyword.get(opts, :existing_error_count, 0)
     max_errors = Keyword.get(opts, :max_errors, @default_max_errors)
     actor = Keyword.get(opts, :actor, SystemActor.get_system_actor())
+    fee_type_map = Keyword.get(opts, :fee_type_map, %{})
+    groups_found = Keyword.get(opts, :groups_found, [])
 
-    {inserted, failed, errors, _collected_error_count, truncated?} =
-      Enum.reduce(chunk_rows_with_lines, {0, 0, [], 0, false}, fn {line_number, row_map},
-                                                                  {acc_inserted, acc_failed,
-                                                                   acc_errors, acc_error_count,
-                                                                   acc_truncated?} ->
+    base_row_opts = %{
+      custom_field_lookup: custom_field_lookup,
+      fee_type_map: fee_type_map,
+      actor: actor
+    }
+
+    {inserted, failed, errors, _collected_error_count, truncated?, warnings, groups_acc} =
+      Enum.reduce(chunk_rows_with_lines, {0, 0, [], 0, false, [], groups_found}, fn {line_number,
+                                                                                     row_map},
+                                                                                    {acc_inserted,
+                                                                                     acc_failed,
+                                                                                     acc_errors,
+                                                                                     acc_error_count,
+                                                                                     acc_truncated?,
+                                                                                     acc_warnings,
+                                                                                     acc_groups} ->
         current_error_count = existing_error_count + acc_error_count
+        row_opts = Map.put(base_row_opts, :groups_found, acc_groups)
 
-        case process_row(row_map, line_number, custom_field_lookup, actor) do
-          {:ok, _member} ->
-            update_inserted(
-              {acc_inserted, acc_failed, acc_errors, acc_error_count, acc_truncated?}
-            )
+        case process_row(row_map, line_number, row_opts) do
+          {:ok, _member, row_warnings, new_groups} ->
+            {new_inserted, new_failed, new_errors, new_error_count, new_truncated?} =
+              update_inserted(
+                {acc_inserted, acc_failed, acc_errors, acc_error_count, acc_truncated?}
+              )
 
-          {:error, error} ->
-            handle_row_error(
-              {acc_inserted, acc_failed, acc_errors, acc_error_count, acc_truncated?},
-              error,
-              current_error_count,
-              max_errors
-            )
+            {new_inserted, new_failed, new_errors, new_error_count, new_truncated?,
+             acc_warnings ++ row_warnings, new_groups}
+
+          {:error, error, new_groups} ->
+            {new_inserted, new_failed, new_errors, new_error_count, new_truncated?} =
+              handle_row_error(
+                {acc_inserted, acc_failed, acc_errors, acc_error_count, acc_truncated?},
+                error,
+                current_error_count,
+                max_errors
+              )
+
+            {new_inserted, new_failed, new_errors, new_error_count, new_truncated?, acc_warnings,
+             new_groups}
         end
       end)
 
@@ -341,7 +420,9 @@ defmodule Mv.Membership.Import.MemberCSV do
        inserted: inserted,
        failed: failed,
        errors: Enum.reverse(errors),
-       errors_truncated?: truncated?
+       errors_truncated?: truncated?,
+       warnings: warnings,
+       groups_found: groups_acc
      }}
   end
 
@@ -505,18 +586,27 @@ defmodule Mv.Membership.Import.MemberCSV do
 
   defp gettext_error_message(_), do: gettext("Email is invalid.")
 
-  # Processes a single row and creates member with custom field values
+  # Processes a single row and creates member with custom field values.
+  # On success returns {:ok, member, warnings, groups}; warnings carry non-fatal
+  # notices such as an unresolved fee-type name. The returned groups list is the
+  # accumulated in-memory group snapshot (seeded from the chunk, grown with any
+  # group created while linking this row) so later rows reuse it instead of
+  # re-reading the whole Group table per row.
   defp process_row(
          row_map,
          line_number,
-         custom_field_lookup,
-         actor
+         %{
+           custom_field_lookup: custom_field_lookup,
+           fee_type_map: fee_type_map,
+           groups_found: groups_found,
+           actor: actor
+         } = _row_opts
        ) do
     # Validate row before database insertion
     case validate_row(row_map, line_number, []) do
       {:error, error} ->
         # Return validation error immediately, no DB insert attempted
-        {:error, error}
+        {:error, error, groups_found}
 
       {:ok, %{member: trimmed_member_attrs, custom: custom_attrs}} ->
         # Prepare custom field values for Ash
@@ -524,20 +614,119 @@ defmodule Mv.Membership.Import.MemberCSV do
           {:error, validation_errors} ->
             # Custom field validation errors - return first error
             first_error = List.first(validation_errors)
-            {:error, %Error{csv_line_number: line_number, field: nil, message: first_error}}
+
+            {:error, %Error{csv_line_number: line_number, field: nil, message: first_error},
+             groups_found}
 
           {:ok, custom_field_values} ->
-            create_member_with_custom_fields(
-              trimmed_member_attrs,
+            {fee_attrs, warnings} =
+              resolve_fee_type_attrs(Map.get(row_map, :fee_type), fee_type_map)
+
+            create_member_and_assign_groups(
+              Map.merge(trimmed_member_attrs, fee_attrs),
               custom_field_values,
+              Map.get(row_map, :groups),
+              groups_found,
               line_number,
-              actor
+              actor,
+              warnings
             )
         end
     end
   rescue
     e ->
-      {:error, %Error{csv_line_number: line_number, field: nil, message: Exception.message(e)}}
+      {:error, %Error{csv_line_number: line_number, field: nil, message: Exception.message(e)},
+       groups_found}
+  end
+
+  # Creates the member, then assigns groups as a post-creation step. A group
+  # assignment failure fails the row (the member was already created, but the
+  # row is reported as failed so the operator can act on it).
+  defp create_member_and_assign_groups(
+         member_attrs,
+         custom_field_values,
+         groups_cell,
+         groups_found,
+         line_number,
+         actor,
+         warnings
+       ) do
+    case create_member_with_custom_fields(
+           member_attrs,
+           custom_field_values,
+           line_number,
+           actor,
+           warnings
+         ) do
+      {:ok, member, member_warnings} ->
+        assign_groups(member, groups_cell, groups_found, line_number, actor, member_warnings)
+
+      {:error, error} ->
+        {:error, error, groups_found}
+    end
+  end
+
+  # Assigns the member to all groups listed in the cell, creating missing groups.
+  # Returns the (possibly grown) group snapshot so the caller can reuse it.
+  defp assign_groups(member, groups_cell, groups_found, line_number, actor, warnings) do
+    names = ColumnResolver.split_group_names(groups_cell)
+
+    Enum.reduce_while(names, {:ok, member, warnings, groups_found}, fn name,
+                                                                       {:ok, _m, _w, acc_groups} ->
+      case link_member_to_group(member, name, acc_groups, actor) do
+        {:ok, group} ->
+          {:cont, {:ok, member, warnings, add_group(acc_groups, group)}}
+
+        {:error, reason} ->
+          {:halt,
+           {:error,
+            %Error{
+              csv_line_number: line_number,
+              field: nil,
+              message: gettext("Group assignment failed: %{reason}", reason: inspect(reason))
+            }, acc_groups}}
+      end
+    end)
+  end
+
+  defp add_group(groups, group) do
+    if Enum.any?(groups, &(&1.id == group.id)), do: groups, else: [group | groups]
+  end
+
+  defp link_member_to_group(member, name, groups_found, actor) do
+    with {:ok, group} <- ColumnResolver.create_or_find_group(name, groups_found, actor),
+         {:ok, _member_group} <-
+           Mv.Membership.create_member_group(
+             %{member_id: member.id, group_id: group.id},
+             actor: actor
+           ) do
+      {:ok, group}
+    end
+  end
+
+  # Resolves the fee-type cell into member attrs plus optional warnings.
+  # Empty cell -> default fee type (SetDefaultMembershipFeeType), no warning.
+  # Matched name -> membership_fee_type_id attr.
+  # Unmatched name -> no attr (default applies), warning naming the value.
+  defp resolve_fee_type_attrs(nil, _fee_type_map), do: {%{}, []}
+
+  defp resolve_fee_type_attrs(cell, fee_type_map) when is_binary(cell) do
+    trimmed = String.trim(cell)
+
+    if trimmed == "" do
+      {%{}, []}
+    else
+      case Map.get(fee_type_map, ColumnResolver.normalize_fee_type_name(trimmed)) do
+        nil ->
+          {%{},
+           [
+             gettext("Fee type '%{name}' not found; using the default fee type.", name: trimmed)
+           ]}
+
+        fee_type_id ->
+          {%{membership_fee_type_id: fee_type_id}, []}
+      end
+    end
   end
 
   # Creates a member with custom field values, handling errors appropriately
@@ -545,7 +734,8 @@ defmodule Mv.Membership.Import.MemberCSV do
          trimmed_member_attrs,
          custom_field_values,
          line_number,
-         actor
+         actor,
+         warnings
        ) do
     # Convert empty strings to nil for date fields so Ash accepts them
     member_attrs = sanitize_date_fields(trimmed_member_attrs)
@@ -565,7 +755,7 @@ defmodule Mv.Membership.Import.MemberCSV do
 
     case Mv.Membership.create_member(final_attrs, actor: actor) do
       {:ok, member} ->
-        {:ok, member}
+        {:ok, member, warnings}
 
       {:error, %Ash.Error.Invalid{} = error} ->
         # Extract email from final_attrs for better error messages

lib/mv_web/controllers/import_template_controller.ex

@@ -0,0 +1,120 @@
+defmodule MvWeb.ImportTemplateController do
+  @moduledoc """
+  Serves CSV import templates generated on the fly from the current custom fields.
+
+  Two actions provide an English (`en/2`) and a German (`de/2`) template. Each
+  template has a single header row listing the standard member columns followed
+  by every existing custom field name (exact match, as the import expects), plus
+  the importable groups and fee-type columns. A single placeholder example row is
+  included to illustrate the format.
+
+  Both actions require the same authorization as the import page
+  (`can?(:create, Member)`); unauthorized requests are rejected.
+  """
+  use MvWeb, :controller
+
+  alias Mv.Authorization.Actor
+  alias Mv.Membership.Member
+  alias Mv.Membership.MembersCSV
+  alias MvWeb.Authorization
+
+  # Standard member columns in template order, with their English and German headers
+  # and a placeholder example value. Groups and fee type are importable extras.
+  @columns [
+    {"first name", "Vorname", "John", "Max"},
+    {"last name", "Nachname", "Doe", "Mustermann"},
+    {"email", "E-Mail", "john.doe@example.com", "max.mustermann@example.com"},
+    {"country", "Land", "Germany", "Deutschland"},
+    {"city", "Stadt", "Berlin", "Berlin"},
+    {"street", "Straße", "Main Street", "Hauptstraße"},
+    {"house number", "Hausnummer", "1a", "12"},
+    {"postal_code", "PLZ", "12345", "10115"},
+    {"join_date", "Beitrittsdatum", "2020-01-15", "2020-01-15"},
+    {"exit_date", "Austrittsdatum", "", ""},
+    {"notes", "Notizen", "", ""},
+    {"membership_fee_start_date", "Beitragsbeginn", "", ""},
+    {"Groups", "Gruppen", "", ""},
+    {"Fee Type", "Beitragsart", "", ""}
+  ]
+
+  @spec en(Plug.Conn.t(), map()) :: Plug.Conn.t()
+  def en(conn, _params) do
+    serve_template(conn, :en, "member_import_en.csv")
+  end
+
+  @spec de(Plug.Conn.t(), map()) :: Plug.Conn.t()
+  def de(conn, _params) do
+    serve_template(conn, :de, "member_import_de.csv")
+  end
+
+  defp serve_template(conn, locale, filename) do
+    actor = current_actor(conn)
+
+    if Authorization.can?(actor, :create, Member) do
+      csv = build_csv(locale, actor)
+
+      send_download(conn, {:binary, csv},
+        filename: filename,
+        content_type: "text/csv; charset=utf-8"
+      )
+    else
+      return_forbidden(conn)
+    end
+  end
+
+  defp build_csv(locale, actor) do
+    custom_field_names = custom_field_names(actor)
+
+    header =
+      Enum.map(@columns, &header_for(&1, locale)) ++ custom_field_names
+
+    example =
+      Enum.map(@columns, &example_for(&1, locale)) ++ Enum.map(custom_field_names, fn _ -> "" end)
+
+    [csv_row(header), csv_row(example)]
+    |> Enum.join("\n")
+  end
+
+  defp header_for({en, _de, _ex_en, _ex_de}, :en), do: en
+  defp header_for({_en, de, _ex_en, _ex_de}, :de), do: de
+
+  defp example_for({_en, _de, ex_en, _ex_de}, :en), do: ex_en
+  defp example_for({_en, _de, _ex_en, ex_de}, :de), do: ex_de
+
+  defp custom_field_names(actor) do
+    Mv.Membership.list_custom_fields!(actor: actor)
+    |> Enum.map(& &1.name)
+  end
+
+  # Serializes a row using the semicolon delimiter (the import auto-detects it),
+  # quoting any field that contains a delimiter, quote, or newline.
+  defp csv_row(fields) do
+    Enum.map_join(fields, ";", &escape_field/1)
+  end
+
+  # Neutralizes spreadsheet formula triggers (the same guard the export writer
+  # applies) before RFC 4180 quoting, so a custom-field name like
+  # `=HYPERLINK(...)` is not evaluated when the template is opened.
+  defp escape_field(field) do
+    field = field |> to_string() |> MembersCSV.safe_cell()
+
+    if String.contains?(field, [";", "\"", "\n", "\r"]) do
+      "\"" <> String.replace(field, "\"", "\"\"") <> "\""
+    else
+      field
+    end
+  end
+
+  defp current_actor(conn) do
+    conn.assigns[:current_user]
+    |> Actor.ensure_loaded()
+  end
+
+  defp return_forbidden(conn) do
+    conn
+    |> put_status(403)
+    |> put_resp_content_type("application/json")
+    |> json(%{error: "Forbidden"})
+    |> halt()
+  end
+end

lib/mv_web/helpers/join_description_renderer.ex

@@ -0,0 +1,70 @@
+defmodule MvWeb.Helpers.JoinDescriptionRenderer do
+  @moduledoc """
+  Renders a custom field's `join_description` into Phoenix-safe HTML for the
+  public join form.
+
+  The renderer auto-links two patterns into `<a href="...">` tags:
+
+  - Markdown links of the form `[text](url)` (processed first)
+  - bare `http(s)://` URLs in the remaining text
+
+  All other content is HTML-escaped: only `<a href="...">` tags are ever
+  emitted, so arbitrary HTML in the input is rendered as inert text. This is a
+  defense-in-depth measure — `join_description` is admin-set content, never
+  end-user input — but the renderer must not become a vector for injecting
+  arbitrary markup.
+
+  Markdown links are matched before bare URLs and their matched region is
+  consumed, so a Markdown link whose URL also looks like a bare URL is linked
+  exactly once (no nested anchors).
+  """
+
+  @markdown_link ~r/\[([^\]]+)\]\((https?:\/\/[^\s)]+)\)/
+  @bare_url ~r/(https?:\/\/[^\s<]+)/
+  @bare_url_anchored ~r/\A(https?:\/\/[^\s<]+)\z/
+
+  @doc """
+  Converts `value` to a Phoenix-safe HTML iolist.
+
+  Returns `{:safe, ""}` for `nil`. For a string, returns `{:safe, iolist}` with
+  links rendered and all other text HTML-escaped.
+  """
+  @spec render(String.t() | nil) :: Phoenix.HTML.safe()
+  def render(nil), do: {:safe, ""}
+
+  def render(value) when is_binary(value) do
+    {:safe, render_segments(value)}
+  end
+
+  # Split on Markdown links first; for each non-Markdown segment, link bare URLs;
+  # everything that is not a link is HTML-escaped.
+  defp render_segments(text) do
+    Regex.split(@markdown_link, text, include_captures: true)
+    |> Enum.map(&render_markdown_or_plain/1)
+  end
+
+  defp render_markdown_or_plain(segment) do
+    case Regex.run(@markdown_link, segment) do
+      [^segment, label, url] -> anchor(url, label)
+      _ -> render_plain(segment)
+    end
+  end
+
+  # Auto-link bare URLs in a plain-text segment, escaping all surrounding text.
+  defp render_plain(segment) do
+    Regex.split(@bare_url, segment, include_captures: true)
+    |> Enum.map(fn part ->
+      if Regex.match?(@bare_url_anchored, part) do
+        anchor(part, part)
+      else
+        escape(part)
+      end
+    end)
+  end
+
+  defp anchor(url, label) do
+    ["<a href=\"", escape(url), "\" class=\"link link-primary\">", escape(label), "</a>"]
+  end
+
+  defp escape(text), do: Phoenix.HTML.html_escape(text) |> Phoenix.HTML.safe_to_string()
+end

lib/mv_web/live/custom_field_live/form_component.ex

@@ -91,6 +91,45 @@ defmodule MvWeb.CustomFieldLive.FormComponent do
           <% end %>
 
           <.input field={@form[:description]} type="text" label={gettext("Description")} />
+
+          <fieldset class="mb-2 fieldset">
+            <label>
+              <span class="mb-1 label flex items-center gap-2">
+                {gettext("Description for join form")}
+                <.tooltip
+                  content={
+                    gettext(
+                      "You can add links: full addresses (https://…) or as [link text](https://…)."
+                    )
+                  }
+                  position="right"
+                >
+                  <span
+                    data-testid="join-description-link-hint"
+                    aria-label={
+                      gettext(
+                        "You can add links: full addresses (https://…) or as [link text](https://…)."
+                      )
+                    }
+                  >
+                    <.icon
+                      name="hero-information-circle"
+                      class="w-4 h-4 text-base-content/60 cursor-help"
+                      aria-hidden="true"
+                    />
+                  </span>
+                </.tooltip>
+              </span>
+              <input
+                type="text"
+                name={@form[:join_description].name}
+                id={@form[:join_description].id}
+                value={Phoenix.HTML.Form.normalize_value("text", @form[:join_description].value)}
+                class="w-full input"
+              />
+            </label>
+          </fieldset>
+
           <.input field={@form[:required]} type="checkbox" label={gettext("Required")} />
           <.input
             field={@form[:show_in_overview]}

lib/mv_web/live/import_live.ex

@@ -99,7 +99,12 @@ defmodule MvWeb.ImportLive do
           <.form_section title={gettext("Choose CSV file")}>
             <Components.custom_fields_notice {assigns} />
             <Components.template_links {assigns} />
-            <Components.import_form {assigns} />
+            <%= if @import_status != :preview do %>
+              <Components.import_form {assigns} />
+            <% end %>
+            <%= if @import_status == :preview do %>
+              <Components.preview {assigns} />
+            <% end %>
             <%= if @import_status == :running or @import_status == :done or @import_status == :error do %>
               <Components.import_progress {assigns} />
             <% end %>
@@ -133,6 +138,29 @@ defmodule MvWeb.ImportLive do
     end
   end
 
+  @impl true
+  def handle_event("confirm_import", _params, socket) do
+    case socket.assigns do
+      %{import_state: import_state} when is_map(import_state) ->
+        start_import(socket, import_state)
+
+      _ ->
+        {:noreply,
+         put_flash(socket, :error, gettext("No prepared import to confirm. Please upload again."))}
+    end
+  end
+
+  @impl true
+  def handle_event("cancel_import", _params, socket) do
+    socket =
+      socket
+      |> assign(:import_state, nil)
+      |> assign(:import_progress, nil)
+      |> assign(:import_status, :idle)
+
+    {:noreply, socket}
+  end
+
   # Checks if all prerequisites for starting an import are met.
   #
   # Validates:
@@ -169,10 +197,10 @@ defmodule MvWeb.ImportLive do
     end
   end
 
-  # Processes CSV upload and starts import process.
+  # Processes CSV upload and enters the mapping preview.
   #
-  # Reads the uploaded CSV file, prepares it for import, and initiates
-  # the chunked processing workflow.
+  # Reads the uploaded CSV file and prepares it (read-only at the DB level), then
+  # shows the mapping preview. No member is created until the user confirms.
   @spec process_csv_upload(Phoenix.LiveView.Socket.t()) ::
           {:noreply, Phoenix.LiveView.Socket.t()}
   defp process_csv_upload(socket) do
@@ -181,7 +209,7 @@ defmodule MvWeb.ImportLive do
     with {:ok, content} <- consume_and_read_csv(socket),
          {:ok, import_state} <-
            MemberCSV.prepare(content, max_rows: Config.csv_import_max_rows(), actor: actor) do
-      start_import(socket, import_state)
+      enter_preview(socket, import_state)
     else
       {:error, reason} when is_binary(reason) ->
         {:noreply,
@@ -193,6 +221,19 @@ defmodule MvWeb.ImportLive do
     end
   end
 
+  # Shows the mapping preview without starting any processing.
+  @spec enter_preview(Phoenix.LiveView.Socket.t(), map()) ::
+          {:noreply, Phoenix.LiveView.Socket.t()}
+  defp enter_preview(socket, import_state) do
+    socket =
+      socket
+      |> assign(:import_state, import_state)
+      |> assign(:import_progress, nil)
+      |> assign(:import_status, :preview)
+
+    {:noreply, socket}
+  end
+
   # Starts the import process by initializing progress tracking and scheduling the first chunk.
   @spec start_import(Phoenix.LiveView.Socket.t(), map()) ::
           {:noreply, Phoenix.LiveView.Socket.t()}
@@ -263,7 +304,9 @@ defmodule MvWeb.ImportLive do
       custom_field_lookup: import_state.custom_field_lookup,
       existing_error_count: length(progress.errors),
       max_errors: @max_errors,
-      actor: actor
+      actor: actor,
+      fee_type_map: import_state.fee_type_map,
+      groups_found: import_state.groups_found
     ]
 
     _ =
@@ -324,8 +367,11 @@ defmodule MvWeb.ImportLive do
     new_progress =
       ImportRunner.merge_progress(progress, chunk_result, idx, max_errors: @max_errors)
 
+    new_import_state = ImportRunner.carry_groups_forward(import_state, chunk_result)
+
     socket =
       socket
+      |> assign(:import_state, new_import_state)
       |> assign(:import_progress, new_progress)
       |> assign(:import_status, new_progress.status)
       |> maybe_send_next_chunk(idx, length(import_state.chunks))

lib/mv_web/live/import_live/components.ex

@@ -25,7 +25,22 @@ defmodule MvWeb.ImportLive.Components do
       <div>
         <p class="text-sm mb-2">
           {gettext(
-            "Use the data field name as the CSV column header in your file. Data fields must exist in Mila before importing, because unknown data field columns will be ignored. Groups and membership fees are not supported for import."
+            "Use the data field name as the CSV column header in your file. Data fields must exist in Mila before importing, because unknown data field columns will be ignored."
+          )}
+        </p>
+        <p class="text-sm mb-2">
+          {gettext(
+            "Groups column (recognized headers): Groups, Gruppen, Gruppe. Comma-separated group names are supported and missing groups are created automatically."
+          )}
+        </p>
+        <p class="text-sm mb-2">
+          {gettext(
+            "Fee type column (recognized headers): Fee Type, fee type, fee_type, membership_fee_type, Beitragsart. Unknown fee types fall back to the default."
+          )}
+        </p>
+        <p class="text-sm">
+          {gettext(
+            "Fee status columns (Membership Fee Status, Bezahlstatus, Mitgliedsbeitragsstatus) are always ignored and cannot be imported."
           )}
         </p>
       </div>
@@ -44,20 +59,12 @@ defmodule MvWeb.ImportLive.Components do
       </p>
       <ul class="list-disc list-inside space-y-1">
         <li>
-          <.link
-            href={~p"/templates/member_import_en.csv"}
-            download="member_import_en.csv"
-            class="link link-primary"
-          >
+          <.link href={~p"/admin/import/template/en"} class="link link-primary">
             {gettext("English Template")}
           </.link>
         </li>
         <li>
-          <.link
-            href={~p"/templates/member_import_de.csv"}
-            download="member_import_de.csv"
-            class="link link-primary"
-          >
+          <.link href={~p"/admin/import/template/de"} class="link link-primary">
             {gettext("German Template")}
           </.link>
         </li>
@@ -108,6 +115,194 @@ defmodule MvWeb.ImportLive.Components do
     """
   end
 
+  @doc """
+  Renders the mapping preview shown between upload and processing.
+
+  Shows the column-to-role mapping, up to 3 sample rows, and notices for
+  auto-created groups, unresolved fee types, empty fee-type cells, and unknown
+  columns. Nothing is written until the user confirms.
+  """
+  def preview(assigns) do
+    state = assigns.import_state
+    column_roles = column_roles(state)
+    column_samples = column_samples(state.preview_rows, length(state.headers))
+
+    assigns =
+      assigns
+      |> assign(:column_roles, column_roles)
+      |> assign(:column_samples, column_samples)
+
+    ~H"""
+    <section
+      class="mt-4 space-y-4"
+      data-testid="import-preview"
+      aria-labelledby="import-preview-heading"
+    >
+      <h2 id="import-preview-heading" class="text-lg font-semibold">
+        {gettext("Preview import")}
+      </h2>
+
+      <div class="overflow-x-auto">
+        <table class="table table-sm w-full" data-testid="preview-mapping-table">
+          <thead>
+            <tr>
+              <th>{gettext("Role")}</th>
+              <th>{gettext("Column")}</th>
+              <th class="text-base-content/60">{gettext("Row 1")}</th>
+              <th class="text-base-content/60">{gettext("Row 2")}</th>
+              <th class="text-base-content/60">{gettext("Row 3")}</th>
+            </tr>
+          </thead>
+          <tbody>
+            <%= for {{header, role}, samples} <- Enum.zip(@column_roles, @column_samples) do %>
+              <tr class={role_row_class(role)} data-testid="preview-column-row">
+                <td>
+                  <span class={"badge badge-sm #{role_badge_class(role)}"}>
+                    {role_label(role)}
+                  </span>
+                </td>
+                <td class="font-medium">{header}</td>
+                <%= for sample <- samples do %>
+                  <td class="text-base-content/70 max-w-32 truncate">{sample}</td>
+                <% end %>
+              </tr>
+            <% end %>
+          </tbody>
+        </table>
+      </div>
+
+      <%= if @import_state.groups_to_create != [] do %>
+        <div class="alert alert-info" role="note" data-testid="preview-groups-notice">
+          <.icon name="hero-information-circle" class="size-5" aria-hidden="true" />
+          <div>
+            <p class="text-sm">
+              {gettext("These groups will be created automatically: %{names}",
+                names: Enum.join(@import_state.groups_to_create, ", ")
+              )}
+            </p>
+          </div>
+        </div>
+      <% end %>
+
+      <%= if @import_state.fee_type_warnings != [] do %>
+        <div class="alert alert-warning" role="alert" data-testid="preview-fee-type-warning">
+          <.icon name="hero-exclamation-circle" class="size-5" aria-hidden="true" />
+          <div>
+            <p class="text-sm">
+              {gettext("Unknown fee types (members get the default): %{names}",
+                names: Enum.join(@import_state.fee_type_warnings, ", ")
+              )}
+            </p>
+            <.link
+              navigate={~p"/membership_fee_settings/new_fee_type"}
+              class="link link-primary text-sm"
+            >
+              {gettext("Create fee type")}
+            </.link>
+          </div>
+        </div>
+      <% end %>
+
+      <%= if @import_state.has_empty_fee_type_cells? do %>
+        <div class="alert alert-info" role="note" data-testid="preview-fee-type-info">
+          <.icon name="hero-information-circle" class="size-5" aria-hidden="true" />
+          <div>
+            <p class="text-sm">
+              {gettext("Rows with an empty fee type will get the default fee type.")}
+            </p>
+          </div>
+        </div>
+      <% end %>
+
+      <%= if @import_state.warnings != [] do %>
+        <div class="alert alert-warning" role="alert" data-testid="preview-unknown-warning">
+          <.icon name="hero-information-circle" class="size-5" aria-hidden="true" />
+          <div>
+            <ul class="list-disc list-inside space-y-1 text-sm">
+              <%= for warning <- @import_state.warnings do %>
+                <li>{warning}</li>
+              <% end %>
+            </ul>
+            <.link navigate={~p"/admin/datafields"} class="link link-primary text-sm">
+              {gettext("Create custom field")}
+            </.link>
+          </div>
+        </div>
+      <% end %>
+
+      <div class="flex gap-2">
+        <.button
+          type="button"
+          phx-click="confirm_import"
+          variant="primary"
+          data-testid="confirm-import-button"
+        >
+          {gettext("Confirm and Import")}
+        </.button>
+        <.button type="button" phx-click="cancel_import" data-testid="cancel-import-button">
+          {gettext("Cancel")}
+        </.button>
+      </div>
+    </section>
+    """
+  end
+
+  # Pairs each CSV header with its resolved role for the preview mapping table.
+  defp column_roles(state) do
+    member_indices = MapSet.new(Map.values(state.column_map))
+    custom_indices = MapSet.new(Map.values(state.custom_field_map))
+    ignored_headers = MapSet.new(state.ignored)
+
+    state.headers
+    |> Enum.with_index()
+    |> Enum.map(fn {header, index} ->
+      {header, role_for(index, header, state, member_indices, custom_indices, ignored_headers)}
+    end)
+  end
+
+  defp role_for(index, header, state, member_indices, custom_indices, ignored_headers) do
+    cond do
+      index == state.groups_column_index -> :groups
+      index == state.fee_type_column_index -> :fee_type
+      MapSet.member?(ignored_headers, header) -> :ignored
+      MapSet.member?(member_indices, index) -> :member_field
+      MapSet.member?(custom_indices, index) -> :custom_field
+      true -> :unknown
+    end
+  end
+
+  defp role_label(:member_field), do: gettext("Member field")
+  defp role_label(:custom_field), do: gettext("Custom field")
+  defp role_label(:groups), do: gettext("Groups")
+  defp role_label(:fee_type), do: gettext("Fee type")
+  defp role_label(:ignored), do: gettext("Ignored (system-computed field)")
+  defp role_label(:unknown), do: gettext("Unknown (ignored)")
+
+  defp role_badge_class(:member_field), do: "badge-primary"
+  defp role_badge_class(:custom_field), do: "badge-secondary"
+  defp role_badge_class(:groups), do: "badge-success"
+  defp role_badge_class(:fee_type), do: "badge-warning"
+  defp role_badge_class(:ignored), do: "badge-ghost"
+  defp role_badge_class(:unknown), do: "badge-error"
+
+  defp role_row_class(:ignored), do: "opacity-50"
+  defp role_row_class(:unknown), do: "opacity-50"
+  defp role_row_class(_), do: nil
+
+  defp column_samples([], col_count), do: List.duplicate([], col_count)
+
+  defp column_samples(rows, col_count) do
+    Enum.map(0..(col_count - 1), fn col_idx ->
+      rows
+      |> Enum.map(fn row -> Enum.at(row, col_idx, "") end)
+      |> pad_to(3, "")
+    end)
+  end
+
+  defp pad_to(list, target, fill) do
+    list ++ List.duplicate(fill, max(0, target - length(list)))
+  end
+
   @doc """
   Renders import progress text and, when done or aborted, the import results section.
   """
@@ -254,8 +449,10 @@ defmodule MvWeb.ImportLive.Components do
   @doc """
   Returns whether the Start Import button should be disabled.
   """
-  @spec import_button_disabled?(:idle | :running | :done | :error, [map()]) :: boolean()
+  @spec import_button_disabled?(:idle | :preview | :running | :done | :error, [map()]) ::
+          boolean()
   def import_button_disabled?(:running, _entries), do: true
+  def import_button_disabled?(:preview, _entries), do: true
   def import_button_disabled?(_status, []), do: true
   def import_button_disabled?(_status, [entry | _]) when not entry.done?, do: true
   def import_button_disabled?(_status, _entries), do: false

lib/mv_web/live/join_live.ex

@@ -8,6 +8,7 @@ defmodule MvWeb.JoinLive do
   alias Ash.Resource.Info
   alias Mv.Membership
   alias Mv.Membership.CustomFieldLookup
+  alias MvWeb.Helpers.JoinDescriptionRenderer
   alias MvWeb.JoinRateLimit
   alias MvWeb.Translations.MemberFields
 
@@ -96,14 +97,20 @@ defmodule MvWeb.JoinLive do
                           class="checkbox checkbox-sm"
                         />
                         <span class="label-text">
-                          {field.label}<span :if={field.required} aria-hidden="true"> *</span>
+                          {render_field_label(field)}<span
+                            :if={field.required}
+                            aria-hidden="true"
+                          > *</span>
                         </span>
                       </label>
                     <% else %>
                       <div>
                         <label for={"join-field-#{field.id}"} class="label">
                           <span class="label-text">
-                            {field.label}<span :if={field.required} aria-hidden="true"> *</span>
+                            {render_field_label(field)}<span
+                              :if={field.required}
+                              aria-hidden="true"
+                            > *</span>
                           </span>
                         </label>
                         <input
@@ -237,6 +244,17 @@ defmodule MvWeb.JoinLive do
      |> assign(:form, to_form(params, as: "join"))}
   end
 
+  # Renders a join field's label. When a custom field has a join_description it is
+  # rendered with auto-linked URLs/Markdown; otherwise the plain field label is used.
+  # Safe: join_description is admin-set settings content, never end-user input, and
+  # JoinDescriptionRenderer escapes all non-link text (only emits <a href> tags).
+  defp render_field_label(%{join_description: join_description})
+       when is_binary(join_description) do
+    JoinDescriptionRenderer.render(join_description)
+  end
+
+  defp render_field_label(%{label: label}), do: label
+
   defp build_join_fields_with_labels(allowlist) do
     member_field_strings = Mv.Constants.member_fields() |> Enum.map(&Atom.to_string/1)
     custom_field_by_id = custom_field_map(allowlist, member_field_strings)
@@ -249,20 +267,36 @@ defmodule MvWeb.JoinLive do
   defp build_join_field(id, required, member_field_strings, custom_field_by_id) do
     if id in member_field_strings do
       label = MemberFields.label(String.to_existing_atom(id))
-      %{id: id, label: label, required: required, input_type: member_field_input_type(id)}
+
+      %{
+        id: id,
+        label: label,
+        required: required,
+        input_type: member_field_input_type(id),
+        join_description: nil
+      }
     else
       custom_field = Map.get(custom_field_by_id, id)
       label = if custom_field, do: custom_field.name, else: gettext("Field")
       input_type = custom_field_input_type(custom_field && custom_field.value_type)
 
-      %{id: id, label: label, required: required, input_type: input_type}
+      %{
+        id: id,
+        label: label,
+        required: required,
+        input_type: input_type,
+        join_description: custom_field && custom_field.join_description
+      }
     end
   end
 
   defp custom_field_map(allowlist, _member_field_strings) do
     allowlist
     |> Enum.map(& &1.id)
-    |> CustomFieldLookup.fetch_map_by_ids(authorize?: false, select: [:id, :name, :value_type])
+    |> CustomFieldLookup.fetch_map_by_ids(
+      authorize?: false,
+      select: [:id, :name, :value_type, :join_description]
+    )
   end
 
   defp initial_form_params(join_fields) do

lib/mv_web/live/member_live/show.ex

@@ -235,6 +235,19 @@ defmodule MvWeb.MemberLive.Show do
                       <%= for custom_field <- @custom_fields do %>
                         <% cfv = find_custom_field_value(@member.custom_field_values, custom_field.id) %>
                         <.data_field label={custom_field.name}>
+                          <:label_suffix :if={custom_field.join_description}>
+                            <.tooltip
+                              content={"#{gettext("Join form:")} #{custom_field.join_description}"}
+                              wrap_class="ml-1 inline-flex items-center"
+                            >
+                              <span data-testid="join-description-tooltip">
+                                <.icon
+                                  name="hero-information-circle"
+                                  class="size-3.5 text-base-content/50"
+                                />
+                              </span>
+                            </.tooltip>
+                          </:label_suffix>
                           {format_custom_field_value(cfv, custom_field.value_type)}
                         </.data_field>
                       <% end %>
@@ -605,11 +618,14 @@ defmodule MvWeb.MemberLive.Show do
   attr :value, :string, default: nil
   attr :class, :string, default: ""
   slot :inner_block
+  slot :label_suffix
 
   defp data_field(assigns) do
     ~H"""
     <dl class={@class}>
-      <dt class="text-sm font-medium text-base-content/70">{@label}</dt>
+      <dt class="text-sm font-medium text-base-content/70 flex items-center">
+        {@label}{render_slot(@label_suffix)}
+      </dt>
       <dd class="mt-1 text-base-content">
         <%= if @inner_block != [] do %>
           {render_slot(@inner_block)}

lib/mv_web/router.ex

@@ -102,6 +102,10 @@ defmodule MvWeb.Router do
       # Import (Admin only)
       live "/admin/import", ImportLive
 
+      # Dynamic CSV import templates (admin only; generated from current custom fields)
+      get "/admin/import/template/en", ImportTemplateController, :en
+      get "/admin/import/template/de", ImportTemplateController, :de
+
       post "/members/export.csv", MemberExportController, :export
       post "/members/export.pdf", MemberPdfExportController, :export
       post "/set_locale", LocaleController, :set_locale