CODE_GUIDELINES.md

@@ -89,7 +89,8 @@ lib/
 │   ├── join_request/      # JoinRequest changes (SetConfirmationToken, ConfirmRequest)
 │   ├── custom_field.ex               # Custom field (definition) resource
 │   ├── custom_field_value.ex        # Custom field value resource
-│   ├── setting.ex         # Global settings (singleton resource)
+│   ├── setting.ex         # Global settings (singleton resource; incl. join form config)
+│   ├── setting/           # Setting changes (NormalizeJoinFormSettings, etc.)
 │   ├── group.ex           # Group resource
 │   ├── member_group.ex    # MemberGroup join table resource
 │   └── email.ex           # Email custom type
@@ -1139,6 +1140,12 @@ let liveSocket = new LiveSocket("/live", Socket, {
 })
 ```
 
+**Vendor assets (third-party JS):**
+
+Some JavaScript libraries are committed as vendored files in `assets/vendor/` (e.g. `topbar`, `sortable.js`) when they are not available as npm packages or we need a specific build. Document their origin and how to update them:
+
+- **Sortable.js** (`assets/vendor/sortable.js`): From [SortableJS](https://github.com/SortableJS/Sortable), version noted in the file header (e.g. `/*! Sortable 1.15.6 - MIT ... */`). To update: download the desired release from the repo and replace the file; keep the header comment for traceability.
+
 ### 3.8 Code Quality: Credo
 
 **Static Code Analysis:**

assets/css/app.css

@@ -656,3 +656,34 @@
 }
 
 /* This file is for your main application CSS */
+
+/* ============================================
+   SortableList: drag-and-drop table rows
+   ============================================ */
+
+/* Ghost row: placeholder showing where the dragged item will be dropped.
+   Background fills the gap; text invisible so layout matches original row. */
+.sortable-ghost {
+  background-color: var(--color-base-300) !important;
+  opacity: 0.5;
+}
+.sortable-ghost td {
+  border-color: transparent !important;
+}
+
+/* Chosen row: the row being actively dragged (follows the cursor). */
+.sortable-chosen {
+  background-color: var(--color-base-200);
+  box-shadow: 0 4px 16px -2px oklch(0 0 0 / 0.18);
+  cursor: grabbing !important;
+}
+
+/* Drag handle button: only grab cursor, no hover effect for mouse users.
+   Keyboard outline is handled via JS outline style. */
+[data-sortable-handle] button {
+  cursor: grab;
+}
+[data-sortable-handle] button:hover {
+  background-color: transparent !important;
+  color: inherit;
+}

assets/js/app.js

@@ -21,6 +21,7 @@ import "phoenix_html"
 import {Socket} from "phoenix"
 import {LiveSocket} from "phoenix_live_view"
 import topbar from "../vendor/topbar"
+import Sortable from "../vendor/sortable"
 
 let csrfToken = document.querySelector("meta[name='csrf-token']").getAttribute("content")
 
@@ -120,6 +121,148 @@ Hooks.TabListKeydown = {
   }
 }
 
+// SortableList hook: Accessible reorderable table/list.
+// Mouse drag: SortableJS (smooth animation, ghost row, items push apart).
+// Keyboard: Space = grab/drop, Arrow up/down = move, Escape = cancel, matching the Salesforce a11y pattern.
+// Container must have data-reorder-event and data-list-id.
+// Each row (tr) must have data-row-index; locked rows have data-locked="true".
+// Pushes event with { from_index, to_index } (both integers) on reorder.
+Hooks.SortableList = {
+  mounted() {
+    this.reorderEvent = this.el.dataset.reorderEvent
+    this.listId = this.el.dataset.listId
+    // Keyboard state: store grabbed row id so it survives LiveView re-renders
+    this.grabbedRowId = null
+
+    this.announcementEl = this.listId ? document.getElementById(this.listId + "-announcement") : null
+    const announce = (msg) => {
+      if (!this.announcementEl) return
+      // Clear then re-set to force screen reader re-read
+      this.announcementEl.textContent = ""
+      setTimeout(() => { if (this.announcementEl) this.announcementEl.textContent = msg }, 50)
+    }
+
+    const tbody = this.el.querySelector("tbody")
+    if (!tbody) return
+
+    this.getRows = () => Array.from(tbody.querySelectorAll("tr"))
+    this.getRowIndex = (tr) => {
+      const idx = tr.getAttribute("data-row-index")
+      return idx != null ? parseInt(idx, 10) : -1
+    }
+    this.isLocked = (tr) => tr.getAttribute("data-locked") === "true"
+
+    // SortableJS for mouse drag-and-drop with animation
+    this.sortable = new Sortable(tbody, {
+      animation: 150,
+      handle: "[data-sortable-handle]",
+      // Disable sorting for locked rows (first row = email)
+      filter: "[data-locked='true']",
+      preventOnFilter: true,
+      // Ghost (placeholder showing where the item will land)
+      ghostClass: "sortable-ghost",
+      // The item being dragged
+      chosenClass: "sortable-chosen",
+      // Cursor while dragging
+      dragClass: "sortable-drag",
+      // Don't trigger on handle area clicks (only actual drag)
+      delay: 0,
+      onEnd: (e) => {
+        if (e.oldIndex === e.newIndex) return
+        this.pushEvent(this.reorderEvent, { from_index: e.oldIndex, to_index: e.newIndex })
+        announce(`Dropped. Position ${e.newIndex + 1} of ${this.getRows().length}.`)
+        // LiveView will reconcile the DOM order after re-render
+      }
+    })
+
+    // Keyboard handler (Salesforce a11y pattern: Space=grab/drop, Arrows=move, Escape=cancel)
+    this.handleKeyDown = (e) => {
+      // Don't intercept Space on interactive elements (checkboxes, buttons, inputs)
+      const tag = e.target.tagName
+      if (tag === "INPUT" || tag === "BUTTON" || tag === "SELECT" || tag === "TEXTAREA") return
+
+      const tr = e.target.closest("tr")
+      if (!tr || this.isLocked(tr)) return
+      const rows = this.getRows()
+      const idx = this.getRowIndex(tr)
+      if (idx < 0) return
+      const total = rows.length
+
+      if (e.key === " ") {
+        e.preventDefault()
+        const rowId = tr.id
+        if (this.grabbedRowId === rowId) {
+          // Drop
+          this.grabbedRowId = null
+          tr.style.outline = ""
+          announce(`Dropped. Position ${idx + 1} of ${total}.`)
+        } else {
+          // Grab
+          this.grabbedRowId = rowId
+          tr.style.outline = "2px solid var(--color-primary)"
+          tr.style.outlineOffset = "-2px"
+          announce(`Grabbed. Position ${idx + 1} of ${total}. Use arrow keys to move, Space to drop, Escape to cancel.`)
+        }
+        return
+      }
+
+      if (e.key === "Escape") {
+        if (this.grabbedRowId != null) {
+          e.preventDefault()
+          const grabbedTr = document.getElementById(this.grabbedRowId)
+          if (grabbedTr) { grabbedTr.style.outline = ""; grabbedTr.style.outlineOffset = "" }
+          this.grabbedRowId = null
+          announce("Reorder cancelled.")
+        }
+        return
+      }
+
+      if (this.grabbedRowId == null) return
+
+      // Do not move into a locked row (e.g. email always first)
+      if (e.key === "ArrowUp" && idx > 0) {
+        const targetRow = rows[idx - 1]
+        if (!this.isLocked(targetRow)) {
+          e.preventDefault()
+          this.pushEvent(this.reorderEvent, { from_index: idx, to_index: idx - 1 })
+          announce(`Position ${idx} of ${total}.`)
+        }
+      } else if (e.key === "ArrowDown" && idx < total - 1) {
+        const targetRow = rows[idx + 1]
+        if (!this.isLocked(targetRow)) {
+          e.preventDefault()
+          this.pushEvent(this.reorderEvent, { from_index: idx, to_index: idx + 1 })
+          announce(`Position ${idx + 2} of ${total}.`)
+        }
+      }
+    }
+
+    this.el.addEventListener("keydown", this.handleKeyDown, true)
+  },
+
+  updated() {
+    // Re-apply keyboard outline and restore focus after LiveView re-render.
+    // LiveView DOM patching loses focus; without explicit re-focus the next keypress
+    // goes to document.body (Space scrolls the page instead of triggering our handler).
+    if (this.grabbedRowId) {
+      const tr = document.getElementById(this.grabbedRowId)
+      if (tr) {
+        tr.style.outline = "2px solid var(--color-primary)"
+        tr.style.outlineOffset = "-2px"
+        tr.focus()
+      } else {
+        // Row no longer exists (removed while grabbed), clear state
+        this.grabbedRowId = null
+      }
+    }
+  },
+
+  destroyed() {
+    if (this.sortable) this.sortable.destroy()
+    this.el.removeEventListener("keydown", this.handleKeyDown, true)
+  }
+}
+
 // SidebarState hook: Manages sidebar expanded/collapsed state
 Hooks.SidebarState = {
   mounted() {

docs/development-progress-log.md

@@ -809,6 +809,14 @@ end
 - **PR review follow-ups (Join confirmation):** Join confirmation email uses `Mailer.deliver/1` and returns `{:ok, email}` \| `{:error, reason}`; domain logs delivery errors but still returns `{:ok, request}` so the user sees success. Comment in `submit_join_request/2` clarifies that the raw token is hashed by `JoinRequest.Changes.SetConfirmationToken`. Cleanup task uses `Ash.bulk_destroy` and logs partial errors without halting. Layout uses assigns `app_name` and `locale` (from config/Gettext) instead of hardcoded "Mila" and `lang="de"`. Production `runtime.exs` sets `:mail_from` from ENV (`MAIL_FROM_NAME`, `MAIL_FROM_EMAIL`). Layout reference unified to `"layout.html"`; redundant `put_layout` removed from senders.
 - Tests: `join_request_test.exs`, `join_request_submit_email_test.exs`, `join_confirm_controller_test.exs` – all pass.
 
+**Subtask 3 – Admin: Join form settings (done):**
+- **Setting resource** (`lib/membership/setting.ex`): 3 new attributes `join_form_enabled` (boolean, default false), `join_form_field_ids` ({:array, :string} – ordered list of member field names or custom field UUIDs), `join_form_field_required` (:map – field ID → boolean). Added to `:create` and `:update` accept lists. Validation rejects field IDs that are neither valid member field names nor UUID format. Migration: `20260310114701_add_join_form_settings_to_settings.exs`.
+- **NormalizeJoinFormSettings** (`lib/membership/setting/changes/normalize_join_form_settings.ex`): Change applied on create/update whenever join form attrs are changing. Ensures email is always in `join_form_field_ids`, forces `join_form_field_required["email"] = true`, drops required flags for fields not in `join_form_field_ids`.
+- **Domain** (`lib/membership/membership.ex`): `Mv.Membership.get_join_form_allowlist/0` – returns `[]` when join form is disabled, otherwise a list of `%{id, required, type}` maps (type = `:member_field` or `:custom_field` based on ID format).
+- **GlobalSettingsLive** (`lib/mv_web/live/global_settings_live.ex`): New "Join Form" / "Beitrittsformular" section between Club Settings and Vereinfacht. Checkbox to enable/disable, table of selected fields (with Required checkbox per field – email always checked/disabled, other fields can be toggled), "Add field" dropdown with all unselected member fields and custom fields, "Save Join Form Settings" button. State is managed locally (not via AshPhoenix.Form); saved on explicit save click.
+- **Translations**: 14 new German strings in `priv/gettext/de/LC_MESSAGES/default.po` (Beitrittsformular, Felder im Beitrittsformular, Feld hinzufügen, etc.).
+- Tests: All 13 tests in `test/membership/setting_join_form_test.exs` pass; full test suite 1900 tests, 0 failures.
+
 ### Test Data Management
 
 **Seed Data:**

lib/membership/membership.ex

@@ -455,6 +455,56 @@ defmodule Mv.Membership do
     end
   end
 
+  @doc """
+  Returns the allowlist of fields configured for the public join form.
+
+  Reads the current settings. When the join form is disabled (or no settings exist),
+  returns an empty list. When enabled, returns each configured field as a map with:
+    - `:id` - field identifier string (member field name or custom field UUID)
+    - `:required` - boolean; email is always true
+    - `:type` - `:member_field` or `:custom_field`
+
+  This is the server-side allowlist used by the join form submit action (Subtask 4)
+  to enforce which fields are accepted from user input.
+
+  ## Returns
+
+    - `[%{id: String.t(), required: boolean(), type: :member_field | :custom_field}]`
+    - `[]` when join form is disabled or settings are missing
+
+  ## Examples
+
+      iex> Mv.Membership.get_join_form_allowlist()
+      [%{id: "email", required: true, type: :member_field},
+       %{id: "first_name", required: false, type: :member_field}]
+
+  """
+  def get_join_form_allowlist do
+    case get_settings() do
+      {:ok, settings} ->
+        if settings.join_form_enabled do
+          build_join_form_allowlist(settings)
+        else
+          []
+        end
+
+      {:error, _} ->
+        []
+    end
+  end
+
+  defp build_join_form_allowlist(settings) do
+    field_ids = settings.join_form_field_ids || []
+    required_config = settings.join_form_field_required || %{}
+    member_field_names = Mv.Constants.member_fields() |> Enum.map(&Atom.to_string/1)
+
+    Enum.map(field_ids, fn id ->
+      type = if id in member_field_names, do: :member_field, else: :custom_field
+      required = Map.get(required_config, id, false)
+      %{id: id, required: required, type: type}
+    end)
+  end
+
   defp expired?(nil), do: true
   defp expired?(expires_at), do: DateTime.compare(expires_at, DateTime.utc_now()) == :lt
 end

lib/membership/setting.ex

@@ -15,6 +15,12 @@ defmodule Mv.Membership.Setting do
     (e.g., `%{"first_name" => true, "last_name" => true}`). Email is always required; other fields default to optional.
   - `include_joining_cycle` - Whether to include the joining cycle in membership fee generation (default: true)
   - `default_membership_fee_type_id` - Default membership fee type for new members (optional)
+  - `join_form_enabled` - Whether the public /join page is active (default: false)
+  - `join_form_field_ids` - Ordered list of field IDs shown on the join form. Each entry is
+    either a member field name string (e.g. "email") or a custom field UUID. Email is always
+    included and always required; normalization enforces this automatically.
+  - `join_form_field_required` - Map of field ID => required boolean for the join form.
+    Email is always forced to true.
 
   ## Singleton Pattern
   This resource uses a singleton pattern - there should only be one settings record.
@@ -54,6 +60,10 @@ defmodule Mv.Membership.Setting do
     domain: Mv.Membership,
     data_layer: AshPostgres.DataLayer
 
+  # Used in join_form_field_ids validation (compile-time to avoid recompiling regex and list on every validation)
+  @uuid_pattern ~r/^[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}$/i
+  @valid_join_form_member_fields Mv.Constants.member_fields() |> Enum.map(&Atom.to_string/1)
+
   postgres do
     table "settings"
     repo Mv.Repo
@@ -86,8 +96,13 @@ defmodule Mv.Membership.Setting do
         :oidc_client_secret,
         :oidc_admin_group_name,
         :oidc_groups_claim,
-        :oidc_only
+        :oidc_only,
+        :join_form_enabled,
+        :join_form_field_ids,
+        :join_form_field_required
       ]
+
+      change Mv.Membership.Setting.Changes.NormalizeJoinFormSettings
     end
 
     update :update do
@@ -110,8 +125,13 @@ defmodule Mv.Membership.Setting do
         :oidc_client_secret,
         :oidc_admin_group_name,
         :oidc_groups_claim,
-        :oidc_only
+        :oidc_only,
+        :join_form_enabled,
+        :join_form_field_ids,
+        :join_form_field_required
       ]
+
+      change Mv.Membership.Setting.Changes.NormalizeJoinFormSettings
     end
 
     update :update_member_field_visibility do
@@ -232,6 +252,33 @@ defmodule Mv.Membership.Setting do
              end,
              on: [:create, :update]
 
+    # Validate join_form_field_ids: each entry must be a known member field name
+    # or a UUID-format string (custom field ID). Normalization (NormalizeJoinFormSettings
+    # change) runs before validations, so email is already present when this runs.
+    validate fn changeset, _context ->
+               field_ids = Ash.Changeset.get_attribute(changeset, :join_form_field_ids)
+
+               if is_list(field_ids) and field_ids != [] do
+                 invalid_ids =
+                   Enum.reject(field_ids, fn id ->
+                     is_binary(id) and
+                       (id in @valid_join_form_member_fields or Regex.match?(@uuid_pattern, id))
+                   end)
+
+                 if Enum.empty?(invalid_ids) do
+                   :ok
+                 else
+                   {:error,
+                    field: :join_form_field_ids,
+                    message:
+                      "Invalid field identifiers: #{inspect(invalid_ids)}. Use member field names or custom field UUIDs."}
+                 end
+               else
+                 :ok
+               end
+             end,
+             on: [:create, :update]
+
     # Validate default_membership_fee_type_id exists if set
     validate fn changeset, context ->
                fee_type_id =
@@ -382,6 +429,30 @@ defmodule Mv.Membership.Setting do
       description "When true and OIDC is configured, sign-in shows only OIDC (password login hidden)"
     end
 
+    # Join form (Beitrittsformular) settings
+    attribute :join_form_enabled, :boolean do
+      allow_nil? false
+      default false
+      public? true
+
+      description "When true, the public /join page is active and new members can submit a request."
+    end
+
+    attribute :join_form_field_ids, {:array, :string} do
+      allow_nil? true
+      default []
+      public? true
+
+      description "Ordered list of field IDs shown on the join form. Each entry is a member field name (e.g. 'email') or a custom field UUID. Email is always present after normalization."
+    end
+
+    attribute :join_form_field_required, :map do
+      allow_nil? true
+      public? true
+
+      description "Map of field ID => required boolean for the join form. Email is always true after normalization."
+    end
+
     timestamps()
   end
 

lib/membership/setting/changes/normalize_join_form_settings.ex

@@ -0,0 +1,60 @@
+defmodule Mv.Membership.Setting.Changes.NormalizeJoinFormSettings do
+  @moduledoc """
+  Ash change that normalizes join form field settings before persist.
+
+  Applied on create and update actions whenever join form attributes are present.
+
+  Rules enforced:
+  - Email is always added to join_form_field_ids if not already present.
+  - Email is always marked as required (true) in join_form_field_required.
+  - Keys in join_form_field_required that are not in join_form_field_ids are dropped.
+
+  Only runs when join_form_field_ids is being changed; if only
+  join_form_field_required changes, normalization still uses the current
+  (possibly changed) field_ids to strip orphaned required flags.
+  """
+  use Ash.Resource.Change
+
+  def change(changeset, _opts, _context) do
+    changing_ids? = Ash.Changeset.changing_attribute?(changeset, :join_form_field_ids)
+    changing_required? = Ash.Changeset.changing_attribute?(changeset, :join_form_field_required)
+
+    if changing_ids? or changing_required? do
+      normalize(changeset)
+    else
+      changeset
+    end
+  end
+
+  defp normalize(changeset) do
+    field_ids = Ash.Changeset.get_attribute(changeset, :join_form_field_ids)
+    required_config = Ash.Changeset.get_attribute(changeset, :join_form_field_required)
+
+    field_ids = normalize_field_ids(field_ids)
+    required_config = normalize_required(field_ids, required_config)
+
+    changeset
+    |> Ash.Changeset.force_change_attribute(:join_form_field_ids, field_ids)
+    |> Ash.Changeset.force_change_attribute(:join_form_field_required, required_config)
+  end
+
+  defp normalize_field_ids(nil), do: ["email"]
+
+  defp normalize_field_ids(ids) when is_list(ids) do
+    if "email" in ids do
+      ids
+    else
+      ["email" | ids]
+    end
+  end
+
+  defp normalize_field_ids(_), do: ["email"]
+
+  defp normalize_required(field_ids, required_config) do
+    base = if is_map(required_config), do: required_config, else: %{}
+
+    base
+    |> Map.take(field_ids)
+    |> Map.put("email", true)
+  end
+end

lib/mv_web/components/core_components.ex

@@ -1150,6 +1150,124 @@ defmodule MvWeb.CoreComponents do
 
   defp table_th_sticky_class(_), do: nil
 
+  @doc """
+  Renders a reorderable table (sortable list) with drag handle and keyboard support.
+
+  Uses the SortableList hook for accessible drag-and-drop and keyboard reorder
+  (Space to grab/drop, Arrow up/down to move, Escape to cancel). Pushes the
+  given reorder event with `from_index` and `to_index`; the parent LiveView
+  should reorder the list and re-render.
+
+  ## Attributes
+
+    * `:id` – Required. Unique id for the list (used for hook and live region).
+    * `:rows` – Required. List of row data.
+    * `:row_id` – Required. Function to get a unique id for each row (e.g. for locked_ids).
+    * `:locked_ids` – List of row ids that cannot be reordered (e.g. `["join-field-email"]`). Default `[]`.
+    * `:reorder_event` – Required. LiveView event name to push on reorder (payload: `%{from_index: i, to_index: j}`).
+    * `:row_item` – Function to map row before passing to slots. Default `&Function.identity/1`.
+
+  ## Slots
+
+    * `:col` – Data columns (attr `:label`, `:class`). Content is rendered with the row item.
+    * `:action` – Optional. Last column (e.g. delete button) with the row item.
+
+  ## Examples
+
+      <.sortable_table
+        id="join-form-fields"
+        rows={@join_form_fields}
+        row_id={fn f -> "join-field-\#{f.id}" end}
+        locked_ids={["join-field-email"]}
+        reorder_event="reorder_join_form_field"
+      >
+        <:col :let={field} label={gettext("Field")} class="min-w-[14rem]">{field.label}</:col>
+        <:col :let={field} label={gettext("Required")}>...</:col>
+        <:action :let={field}><.button>Remove</.button></:action>
+      </.sortable_table>
+  """
+  attr :id, :string, required: true
+  attr :rows, :list, required: true
+  attr :row_id, :any, required: true
+  attr :locked_ids, :list, default: []
+  attr :reorder_event, :string, required: true
+  attr :row_item, :any, default: &Function.identity/1
+
+  slot :col, required: true do
+    attr :label, :string, required: true
+    attr :class, :string
+  end
+
+  slot :action
+
+  def sortable_table(assigns) do
+    assigns = assign(assigns, :locked_set, MapSet.new(assigns.locked_ids))
+
+    ~H"""
+    <div
+      id={@id}
+      phx-hook="SortableList"
+      data-reorder-event={@reorder_event}
+      data-locked-ids={Jason.encode!(@locked_ids)}
+      data-list-id={@id}
+      class="overflow-auto"
+    >
+      <span
+        id={"#{@id}-announcement"}
+        aria-live="assertive"
+        aria-atomic="true"
+        class="sr-only"
+      />
+      <table class="table table-zebra">
+        <thead>
+          <tr>
+            <th class="w-10" aria-label={gettext("Reorder")}></th>
+            <th :for={col <- @col} class={Map.get(col, :class)}>{col[:label]}</th>
+            <th :if={@action != []} class="w-0 font-semibold">{gettext("Actions")}</th>
+          </tr>
+        </thead>
+        <tbody>
+          <tr
+            :for={{row, idx} <- Enum.with_index(@rows)}
+            id={@row_id.(row)}
+            data-row-index={idx}
+            data-locked={if(MapSet.member?(@locked_set, @row_id.(row)), do: "true", else: nil)}
+            tabindex={if(not MapSet.member?(@locked_set, @row_id.(row)), do: "0", else: nil)}
+          >
+            <td class="w-10 align-middle" data-sortable-handle>
+              <span
+                :if={MapSet.member?(@locked_set, @row_id.(row))}
+                class="inline-block w-6 text-base-content/20"
+                aria-hidden="true"
+              >
+                <.icon name="hero-bars-3" class="size-4" />
+              </span>
+              <span
+                :if={not MapSet.member?(@locked_set, @row_id.(row))}
+                class="inline-flex items-center justify-center w-6 h-6 cursor-grab text-base-content/40"
+                aria-hidden="true"
+              >
+                <.icon name="hero-bars-3" class="size-4" />
+              </span>
+            </td>
+            <td
+              :for={col <- @col}
+              class={["max-w-xs", Map.get(col, :class) || ""] |> Enum.join(" ")}
+            >
+              {render_slot(col, @row_item.(row))}
+            </td>
+            <td :if={@action != []} class="w-0 font-semibold">
+              <%= for action <- @action do %>
+                {render_slot(action, @row_item.(row))}
+              <% end %>
+            </td>
+          </tr>
+        </tbody>
+      </table>
+    </div>
+    """
+  end
+
   @doc """
   Renders a data list.
 

lib/mv_web/live/global_settings_live.ex

@@ -4,16 +4,24 @@ defmodule MvWeb.GlobalSettingsLive do
 
   ## Features
   - Edit the association/club name
+  - Configure the public join form (Beitrittsformular)
   - Manage custom fields
   - Real-time form validation
   - Success/error feedback
 
   ## Settings
   - `club_name` - The name of the association/club (required)
+  - `join_form_enabled` - Whether the public /join page is active
+  - `join_form_field_ids` - Ordered list of field IDs shown on the join form
+  - `join_form_field_required` - Map of field ID => required boolean
 
   ## Events
-  - `validate` - Real-time form validation
+  - `validate` / `save` - Club settings form
-  - `save` - Save settings changes
+  - `toggle_join_form_enabled` - Enable/disable the join form
+  - `add_join_form_field` / `remove_join_form_field` - Manage join form fields
+  - `toggle_join_form_field_required` - Toggle required flag per field
+  - `toggle_add_field_dropdown` / `hide_add_field_dropdown` - Dropdown visibility
+  - Join form changes (enable/disable, add/remove fields, required toggles) are persisted immediately
 
   ## Note
   Settings is a singleton resource - there is only one settings record.
@@ -31,6 +39,7 @@ defmodule MvWeb.GlobalSettingsLive do
   alias Mv.Membership
   alias Mv.Membership.Member, as: MemberResource
   alias MvWeb.Helpers.MemberHelpers
+  alias MvWeb.Translations.MemberFields
 
   on_mount {MvWeb.LiveHelpers, :ensure_user_role_loaded}
 
@@ -42,6 +51,9 @@ defmodule MvWeb.GlobalSettingsLive do
     locale = session["locale"] || Application.get_env(:mv, :default_locale, "de")
     Gettext.put_locale(MvWeb.Gettext, locale)
 
+    actor = MvWeb.LiveHelpers.current_actor(socket)
+    custom_fields = load_custom_fields(actor)
+
     socket =
       socket
       |> assign(:page_title, gettext("Settings"))
@@ -65,6 +77,7 @@ defmodule MvWeb.GlobalSettingsLive do
       |> assign(:oidc_only_env_set, Mv.Config.oidc_only_env_set?())
       |> assign(:oidc_configured, Mv.Config.oidc_configured?())
       |> assign(:oidc_client_secret_set, present?(settings.oidc_client_secret))
+      |> assign_join_form_state(settings, custom_fields)
       |> assign_form()
 
     {:ok, socket}
@@ -103,6 +116,159 @@ defmodule MvWeb.GlobalSettingsLive do
           </.button>
         </.form>
       </.form_section>
+      <%!-- Join Form Section (Beitrittsformular) --%>
+      <.form_section title={gettext("Join Form")}>
+        <p class="text-sm text-base-content/70 mb-4">
+          {gettext("Configure the public join form that allows new members to submit a join request.")}
+        </p>
+
+        <%!-- Enable/disable --%>
+        <div class="flex items-center gap-3 mb-3">
+          <input
+            type="checkbox"
+            id="join-form-enabled-checkbox"
+            class="checkbox checkbox-sm"
+            checked={@join_form_enabled}
+            phx-click="toggle_join_form_enabled"
+            aria-label={gettext("Join form enabled")}
+          />
+          <label for="join-form-enabled-checkbox" class="cursor-pointer font-medium">
+            {gettext("Join form enabled")}
+          </label>
+        </div>
+
+        <%!-- Board approval (future feature) --%>
+        <div class="flex items-center gap-3 mb-6">
+          <input
+            type="checkbox"
+            id="join-form-board-approval-checkbox"
+            class="checkbox checkbox-sm"
+            checked={false}
+            disabled
+            aria-label={gettext("Board approval required (in development)")}
+          />
+          <label for="join-form-board-approval-checkbox" class="text-base-content/60 font-medium">
+            {gettext("Board approval required (in development)")}
+          </label>
+        </div>
+
+        <div :if={@join_form_enabled}>
+          <%!-- Field list header + Add button (left-aligned) --%>
+          <h3 class="font-medium mb-3">{gettext("Fields on the join form")}</h3>
+          <div class="relative mb-3 w-fit" phx-click-away="hide_add_field_dropdown">
+            <.button
+              type="button"
+              variant="primary"
+              phx-click="toggle_add_field_dropdown"
+              disabled={
+                Enum.empty?(@available_join_form_member_fields) and
+                  Enum.empty?(@available_join_form_custom_fields)
+              }
+              aria-haspopup="listbox"
+              aria-expanded={to_string(@show_add_field_dropdown)}
+            >
+              <.icon name="hero-plus" class="size-4" />
+              {gettext("Add field")}
+            </.button>
+
+            <%!-- Available fields dropdown (sections: Personal data, Custom fields) --%>
+            <div
+              :if={@show_add_field_dropdown}
+              class="absolute left-0 mt-1 w-56 bg-base-100 border border-base-300 rounded-lg shadow-lg z-10 max-h-64 overflow-y-auto"
+              role="listbox"
+              aria-label={gettext("Available fields")}
+            >
+              <div :if={not Enum.empty?(@available_join_form_member_fields)} class="pt-2">
+                <div class="px-4 py-1 text-xs font-semibold text-base-content/60 uppercase tracking-wide">
+                  {gettext("Personal data")}
+                </div>
+                <div
+                  :for={field <- @available_join_form_member_fields}
+                  role="option"
+                  tabindex="0"
+                  class="px-4 py-2 cursor-pointer hover:bg-base-200 text-sm"
+                  phx-click="add_join_form_field"
+                  phx-value-field_id={field.id}
+                >
+                  {field.label}
+                </div>
+              </div>
+              <div
+                :if={not Enum.empty?(@available_join_form_custom_fields)}
+                class={
+                  if(Enum.empty?(@available_join_form_member_fields),
+                    do: "pt-2",
+                    else: "border-t border-base-300"
+                  )
+                }
+              >
+                <div class="px-4 py-1 text-xs font-semibold text-base-content/60 uppercase tracking-wide">
+                  {gettext("Individual fields")}
+                </div>
+                <div
+                  :for={field <- @available_join_form_custom_fields}
+                  role="option"
+                  tabindex="0"
+                  class="px-4 py-2 cursor-pointer hover:bg-base-200 text-sm last:pb-2"
+                  phx-click="add_join_form_field"
+                  phx-value-field_id={field.id}
+                >
+                  {field.label}
+                </div>
+              </div>
+            </div>
+          </div>
+
+          <%!-- Empty state --%>
+          <p :if={Enum.empty?(@join_form_fields)} class="text-sm text-base-content/60 italic mb-4">
+            {gettext("No fields selected. Add at least the email field.")}
+          </p>
+
+          <%!-- Fields table (compact width, reorderable) --%>
+          <div :if={not Enum.empty?(@join_form_fields)} class="mb-4 max-w-2xl">
+            <.sortable_table
+              id="join-form-fields-table"
+              rows={@join_form_fields}
+              row_id={fn field -> "join-field-#{field.id}" end}
+              reorder_event="reorder_join_form_field"
+            >
+              <:col :let={field} label={gettext("Field")} class="min-w-[14rem]">
+                {field.label}
+              </:col>
+              <:col :let={field} label={gettext("Required")} class="w-24 max-w-[9.375rem] text-center">
+                <input
+                  type="checkbox"
+                  class="checkbox checkbox-sm"
+                  checked={field.required}
+                  disabled={not field.can_toggle_required}
+                  phx-click={if field.can_toggle_required, do: "toggle_join_form_field_required"}
+                  phx-value-field_id={field.id}
+                  aria-label={gettext("Required")}
+                />
+              </:col>
+              <:action :let={field}>
+                <.tooltip content={gettext("Remove")} position="left">
+                  <.button
+                    type="button"
+                    variant="danger"
+                    size="sm"
+                    disabled={not field.can_remove}
+                    class={if(not field.can_remove, do: "opacity-50 cursor-not-allowed", else: "")}
+                    phx-click="remove_join_form_field"
+                    phx-value-field_id={field.id}
+                    aria-label={gettext("Remove field %{label}", label: field.label)}
+                  >
+                    <.icon name="hero-trash" class="size-4" />
+                  </.button>
+                </.tooltip>
+              </:action>
+            </.sortable_table>
+            <p class="mt-2 text-sm text-base-content/60">
+              {gettext("The order of rows determines the field order in the join form.")}
+            </p>
+          </div>
+        </div>
+      </.form_section>
       <%!-- Vereinfacht Integration Section --%>
       <.form_section title={gettext("Vereinfacht Integration")}>
         <%= if @vereinfacht_env_configured do %>
@@ -426,6 +592,148 @@ defmodule MvWeb.GlobalSettingsLive do
     end
   end
 
+  # ---- Join form event handlers ----
+
+  @impl true
+  def handle_event("toggle_join_form_enabled", _params, socket) do
+    socket = assign(socket, :join_form_enabled, not socket.assigns.join_form_enabled)
+    {:noreply, persist_join_form_settings(socket)}
+  end
+
+  @impl true
+  def handle_event("toggle_add_field_dropdown", _params, socket) do
+    {:noreply,
+     assign(socket, :show_add_field_dropdown, not socket.assigns.show_add_field_dropdown)}
+  end
+
+  @impl true
+  def handle_event("hide_add_field_dropdown", _params, socket) do
+    {:noreply, assign(socket, :show_add_field_dropdown, false)}
+  end
+
+  @impl true
+  def handle_event("add_join_form_field", %{"field_id" => field_id}, socket) do
+    member_avail = socket.assigns.available_join_form_member_fields
+    custom_avail = socket.assigns.available_join_form_custom_fields
+    current = socket.assigns.join_form_fields
+
+    field_to_add =
+      Enum.find(member_avail, &(&1.id == field_id)) ||
+        Enum.find(custom_avail, &(&1.id == field_id))
+
+    socket =
+      if field_to_add do
+        full_field = %{
+          id: field_to_add.id,
+          label: field_to_add.label,
+          type: field_to_add.type,
+          required: false,
+          can_remove: field_to_add.id != "email",
+          can_toggle_required: field_to_add.id != "email"
+        }
+
+        new_fields = current ++ [full_field]
+        new_member = Enum.reject(member_avail, &(&1.id == field_id))
+        new_custom = Enum.reject(custom_avail, &(&1.id == field_id))
+
+        socket
+        |> assign(:join_form_fields, new_fields)
+        |> assign(:available_join_form_member_fields, new_member)
+        |> assign(:available_join_form_custom_fields, new_custom)
+        |> assign(:show_add_field_dropdown, false)
+      else
+        socket
+      end
+
+    {:noreply, persist_join_form_settings(socket)}
+  end
+
+  @impl true
+  def handle_event("remove_join_form_field", %{"field_id" => field_id}, socket) do
+    if field_id == "email" do
+      {:noreply, socket}
+    else
+      current = socket.assigns.join_form_fields
+      custom_fields = socket.assigns.join_form_custom_fields
+      new_fields = Enum.reject(current, &(&1.id == field_id))
+      new_ids = Enum.map(new_fields, & &1.id)
+
+      %{member_fields: new_member, custom_fields: new_custom} =
+        build_available_join_form_fields(new_ids, custom_fields)
+
+      socket =
+        socket
+        |> assign(:join_form_fields, new_fields)
+        |> assign(:available_join_form_member_fields, new_member)
+        |> assign(:available_join_form_custom_fields, new_custom)
+        |> persist_join_form_settings()
+
+      {:noreply, socket}
+    end
+  end
+
+  @impl true
+  def handle_event("toggle_join_form_field_required", %{"field_id" => "email"}, socket) do
+    {:noreply, socket}
+  end
+
+  @impl true
+  def handle_event("toggle_join_form_field_required", %{"field_id" => field_id}, socket) do
+    new_fields =
+      Enum.map(socket.assigns.join_form_fields, &toggle_required_if_matches(&1, field_id))
+
+    socket = assign(socket, :join_form_fields, new_fields) |> persist_join_form_settings()
+    {:noreply, socket}
+  end
+
+  @impl true
+  def handle_event(
+        "reorder_join_form_field",
+        %{"from_index" => from_idx, "to_index" => to_idx},
+        socket
+      )
+      when is_integer(from_idx) and is_integer(to_idx) do
+    fields = socket.assigns.join_form_fields
+    new_fields = reorder_list(fields, from_idx, to_idx)
+
+    socket =
+      socket
+      |> assign(:join_form_fields, new_fields)
+      |> persist_join_form_settings()
+
+    {:noreply, socket}
+  end
+
+  # Ignore malformed reorder events (e.g. nil indices from aborted drags)
+  def handle_event("reorder_join_form_field", _params, socket), do: {:noreply, socket}
+
+  defp persist_join_form_settings(socket) do
+    settings = socket.assigns.settings
+    field_ids = Enum.map(socket.assigns.join_form_fields, & &1.id)
+
+    required_map =
+      socket.assigns.join_form_fields
+      |> Map.new(fn field -> {field.id, field.required} end)
+
+    attrs = %{
+      join_form_enabled: socket.assigns.join_form_enabled,
+      join_form_field_ids: field_ids,
+      join_form_field_required: required_map
+    }
+
+    case Membership.update_settings(settings, attrs) do
+      {:ok, updated_settings} ->
+        custom_fields = socket.assigns.join_form_custom_fields
+
+        socket
+        |> assign(:settings, updated_settings)
+        |> assign_join_form_state(updated_settings, custom_fields)
+
+      {:error, _error} ->
+        put_flash(socket, :error, gettext("Could not save join form settings."))
+    end
+  end
+
   @vereinfacht_param_keys ~w[vereinfacht_api_url vereinfacht_api_key vereinfacht_club_id vereinfacht_app_url]
 
   defp vereinfacht_params?(params) when is_map(params) do
@@ -709,4 +1017,101 @@ defmodule MvWeb.GlobalSettingsLive do
     </div>
     """
   end
+
+  # ---- Join form helper functions ----
+
+  defp assign_join_form_state(socket, settings, custom_fields) do
+    enabled = settings.join_form_enabled || false
+    raw_ids = settings.join_form_field_ids || []
+    field_ids = if "email" in raw_ids, do: raw_ids, else: ["email" | raw_ids]
+    required_config = settings.join_form_field_required || %{}
+
+    join_form_fields = build_join_form_fields(field_ids, required_config, custom_fields)
+
+    %{member_fields: member_avail, custom_fields: custom_avail} =
+      build_available_join_form_fields(field_ids, custom_fields)
+
+    socket
+    |> assign(:join_form_enabled, enabled)
+    |> assign(:join_form_fields, join_form_fields)
+    |> assign(:available_join_form_member_fields, member_avail)
+    |> assign(:available_join_form_custom_fields, custom_avail)
+    |> assign(:show_add_field_dropdown, false)
+    |> assign(:join_form_custom_fields, custom_fields)
+  end
+
+  defp build_join_form_fields(field_ids, required_config, custom_fields) do
+    Enum.map(field_ids, fn id ->
+      label = join_form_field_label(id, custom_fields)
+      required = if id == "email", do: true, else: Map.get(required_config, id, false)
+      type = if id in member_field_id_strings(), do: :member_field, else: :custom_field
+
+      %{
+        id: id,
+        label: label,
+        required: required,
+        can_remove: id != "email",
+        can_toggle_required: id != "email",
+        type: type
+      }
+    end)
+  end
+
+  defp build_available_join_form_fields(selected_ids, custom_fields) do
+    member_fields =
+      Mv.Constants.member_fields()
+      |> Enum.reject(fn field -> Atom.to_string(field) in selected_ids end)
+      |> Enum.map(fn field ->
+        %{id: Atom.to_string(field), label: MemberFields.label(field), type: :member_field}
+      end)
+
+    custom_field_entries =
+      custom_fields
+      |> Enum.reject(fn cf -> cf.id in selected_ids end)
+      |> Enum.map(fn cf ->
+        %{id: cf.id, label: cf.name, type: :custom_field}
+      end)
+      |> Enum.sort_by(& &1.label)
+
+    %{member_fields: member_fields, custom_fields: custom_field_entries}
+  end
+
+  defp join_form_field_label(id, custom_fields) do
+    if id in member_field_id_strings() do
+      MemberFields.label(String.to_existing_atom(id))
+    else
+      case Enum.find(custom_fields, &(&1.id == id)) do
+        nil -> id
+        cf -> cf.name
+      end
+    end
+  end
+
+  defp toggle_required_if_matches(%{id: id} = field, id),
+    do: Map.put(field, :required, not field.required)
+
+  defp toggle_required_if_matches(field, _field_id), do: field
+
+  defp reorder_list(list, from_index, to_index) do
+    item = Enum.at(list, from_index)
+    rest = List.delete_at(list, from_index)
+    List.insert_at(rest, to_index, item)
+  end
+
+  defp member_field_id_strings do
+    Mv.Constants.member_fields() |> Enum.map(&Atom.to_string/1)
+  end
+
+  defp load_custom_fields(nil), do: []
+
+  defp load_custom_fields(actor) do
+    case Ash.read(Mv.Membership.CustomField,
+           actor: actor,
+           domain: Mv.Membership,
+           authorize?: true
+         ) do
+      {:ok, fields} -> fields
+      {:error, _} -> []
+    end
+  end
 end

priv/gettext/de/LC_MESSAGES/default.po

@@ -357,6 +357,7 @@ msgstr "Passwort-Authentifizierung"
 
 #: lib/mv_web/live/custom_field_live/form_component.ex
 #: lib/mv_web/live/custom_field_live/index_component.ex
+#: lib/mv_web/live/global_settings_live.ex
 #: lib/mv_web/live/member_field_live/form_component.ex
 #: lib/mv_web/live/member_field_live/index_component.ex
 #, elixir-autogen, elixir-format
@@ -2149,6 +2150,7 @@ msgstr "Mitglied ist nicht in dieser Gruppe."
 msgid "No email"
 msgstr "Keine E-Mail"
 
+#: lib/mv_web/live/global_settings_live.ex
 #: lib/mv_web/live/group_live/show.ex
 #, elixir-autogen, elixir-format
 msgid "Remove"
@@ -3324,3 +3326,78 @@ msgstr "Unvollständig"
 #, elixir-autogen, elixir-format, fuzzy
 msgid "These fields are necessary for MILA to handle member identification and payment calculations in the future. Thus you cannot delete these fields but hide them in the member overview."
 msgstr "Diese Datenfelder sind für MILA notwendig, um Mitglieder zu identifizieren und zukünftig Beitragszahlungen zu berechnen. Aus diesem Grund können sie nicht gelöscht, aber in der Übersicht ausgeblendet werden."
+
+#: lib/mv_web/live/global_settings_live.ex
+#, elixir-autogen, elixir-format
+msgid "Add field"
+msgstr "Feld hinzufügen"
+
+#: lib/mv_web/live/global_settings_live.ex
+#, elixir-autogen, elixir-format
+msgid "Available fields"
+msgstr "Verfügbare Felder"
+
+#: lib/mv_web/live/global_settings_live.ex
+#, elixir-autogen, elixir-format
+msgid "Configure the public join form that allows new members to submit a join request."
+msgstr "Konfiguriere das öffentliche Beitrittsformular, über das neue Mitglieder einen Beitrittsantrag stellen können."
+
+#: lib/mv_web/live/global_settings_live.ex
+#, elixir-autogen, elixir-format
+msgid "Could not save join form settings."
+msgstr "Beitrittsformular-Einstellungen konnten nicht gespeichert werden."
+
+#: lib/mv_web/live/global_settings_live.ex
+#, elixir-autogen, elixir-format
+msgid "Field"
+msgstr "Feld"
+
+#: lib/mv_web/live/global_settings_live.ex
+#, elixir-autogen, elixir-format
+msgid "Fields on the join form"
+msgstr "Felder im Beitrittsformular"
+
+#: lib/mv_web/live/global_settings_live.ex
+#, elixir-autogen, elixir-format
+msgid "Join Form"
+msgstr "Beitrittsformular"
+
+#: lib/mv_web/live/global_settings_live.ex
+#, elixir-autogen, elixir-format
+msgid "Join form enabled"
+msgstr "Beitrittsformular aktiv"
+
+#: lib/mv_web/live/global_settings_live.ex
+#, elixir-autogen, elixir-format
+msgid "No fields selected. Add at least the email field."
+msgstr "Keine Felder ausgewählt. Füge mindestens das E-Mail-Feld hinzu."
+
+#: lib/mv_web/live/global_settings_live.ex
+#, elixir-autogen, elixir-format
+msgid "Remove field %{label}"
+msgstr "Feld %{label} entfernen"
+
+#: lib/mv_web/live/global_settings_live.ex
+#, elixir-autogen, elixir-format
+msgid "Board approval required (in development)"
+msgstr "Bestätigung durch Vorstand erforderlich (in Entwicklung)"
+
+#: lib/mv_web/live/global_settings_live.ex
+#, elixir-autogen, elixir-format
+msgid "Individual fields"
+msgstr "Individuelle Felder"
+
+#: lib/mv_web/live/global_settings_live.ex
+#, elixir-autogen, elixir-format
+msgid "Personal data"
+msgstr "Persönliche Daten"
+
+#: lib/mv_web/components/core_components.ex
+#, elixir-autogen, elixir-format
+msgid "Reorder"
+msgstr "Umordnen"
+
+#: lib/mv_web/live/global_settings_live.ex
+#, elixir-autogen, elixir-format
+msgid "The order of rows determines the field order in the join form."
+msgstr "Die Reihenfolge der Zeilen bestimmt die Reihenfolge der Felder im Beitrittsformular."

priv/gettext/default.pot

@@ -358,6 +358,7 @@ msgstr ""
 
 #: lib/mv_web/live/custom_field_live/form_component.ex
 #: lib/mv_web/live/custom_field_live/index_component.ex
+#: lib/mv_web/live/global_settings_live.ex
 #: lib/mv_web/live/member_field_live/form_component.ex
 #: lib/mv_web/live/member_field_live/index_component.ex
 #, elixir-autogen, elixir-format
@@ -2150,6 +2151,7 @@ msgstr ""
 msgid "No email"
 msgstr ""
 
+#: lib/mv_web/live/global_settings_live.ex
 #: lib/mv_web/live/group_live/show.ex
 #, elixir-autogen, elixir-format
 msgid "Remove"
@@ -3324,3 +3326,78 @@ msgstr ""
 #, elixir-autogen, elixir-format
 msgid "These fields are necessary for MILA to handle member identification and payment calculations in the future. Thus you cannot delete these fields but hide them in the member overview."
 msgstr ""
+
+#: lib/mv_web/live/global_settings_live.ex
+#, elixir-autogen, elixir-format
+msgid "Add field"
+msgstr ""
+
+#: lib/mv_web/live/global_settings_live.ex
+#, elixir-autogen, elixir-format
+msgid "Available fields"
+msgstr ""
+
+#: lib/mv_web/live/global_settings_live.ex
+#, elixir-autogen, elixir-format
+msgid "Configure the public join form that allows new members to submit a join request."
+msgstr ""
+
+#: lib/mv_web/live/global_settings_live.ex
+#, elixir-autogen, elixir-format
+msgid "Could not save join form settings."
+msgstr ""
+
+#: lib/mv_web/live/global_settings_live.ex
+#, elixir-autogen, elixir-format
+msgid "Field"
+msgstr ""
+
+#: lib/mv_web/live/global_settings_live.ex
+#, elixir-autogen, elixir-format
+msgid "Fields on the join form"
+msgstr ""
+
+#: lib/mv_web/live/global_settings_live.ex
+#, elixir-autogen, elixir-format
+msgid "Join Form"
+msgstr ""
+
+#: lib/mv_web/live/global_settings_live.ex
+#, elixir-autogen, elixir-format
+msgid "Join form enabled"
+msgstr ""
+
+#: lib/mv_web/live/global_settings_live.ex
+#, elixir-autogen, elixir-format
+msgid "No fields selected. Add at least the email field."
+msgstr ""
+
+#: lib/mv_web/live/global_settings_live.ex
+#, elixir-autogen, elixir-format
+msgid "Remove field %{label}"
+msgstr ""
+
+#: lib/mv_web/live/global_settings_live.ex
+#, elixir-autogen, elixir-format
+msgid "Board approval required (in development)"
+msgstr ""
+
+#: lib/mv_web/live/global_settings_live.ex
+#, elixir-autogen, elixir-format
+msgid "Individual fields"
+msgstr ""
+
+#: lib/mv_web/live/global_settings_live.ex
+#, elixir-autogen, elixir-format
+msgid "Personal data"
+msgstr ""
+
+#: lib/mv_web/components/core_components.ex
+#, elixir-autogen, elixir-format
+msgid "Reorder"
+msgstr ""
+
+#: lib/mv_web/live/global_settings_live.ex
+#, elixir-autogen, elixir-format
+msgid "The order of rows determines the field order in the join form."
+msgstr ""

priv/gettext/en/LC_MESSAGES/default.po

@@ -358,6 +358,7 @@ msgstr ""
 
 #: lib/mv_web/live/custom_field_live/form_component.ex
 #: lib/mv_web/live/custom_field_live/index_component.ex
+#: lib/mv_web/live/global_settings_live.ex
 #: lib/mv_web/live/member_field_live/form_component.ex
 #: lib/mv_web/live/member_field_live/index_component.ex
 #, elixir-autogen, elixir-format
@@ -2150,6 +2151,7 @@ msgstr ""
 msgid "No email"
 msgstr ""
 
+#: lib/mv_web/live/global_settings_live.ex
 #: lib/mv_web/live/group_live/show.ex
 #, elixir-autogen, elixir-format
 msgid "Remove"
@@ -3324,3 +3326,78 @@ msgstr ""
 #, elixir-autogen, elixir-format, fuzzy
 msgid "These fields are necessary for MILA to handle member identification and payment calculations in the future. Thus you cannot delete these fields but hide them in the member overview."
 msgstr ""
+
+#: lib/mv_web/live/global_settings_live.ex
+#, elixir-autogen, elixir-format
+msgid "Add field"
+msgstr ""
+
+#: lib/mv_web/live/global_settings_live.ex
+#, elixir-autogen, elixir-format
+msgid "Available fields"
+msgstr ""
+
+#: lib/mv_web/live/global_settings_live.ex
+#, elixir-autogen, elixir-format
+msgid "Configure the public join form that allows new members to submit a join request."
+msgstr ""
+
+#: lib/mv_web/live/global_settings_live.ex
+#, elixir-autogen, elixir-format
+msgid "Could not save join form settings."
+msgstr ""
+
+#: lib/mv_web/live/global_settings_live.ex
+#, elixir-autogen, elixir-format
+msgid "Field"
+msgstr ""
+
+#: lib/mv_web/live/global_settings_live.ex
+#, elixir-autogen, elixir-format
+msgid "Fields on the join form"
+msgstr ""
+
+#: lib/mv_web/live/global_settings_live.ex
+#, elixir-autogen, elixir-format
+msgid "Join Form"
+msgstr ""
+
+#: lib/mv_web/live/global_settings_live.ex
+#, elixir-autogen, elixir-format
+msgid "Join form enabled"
+msgstr ""
+
+#: lib/mv_web/live/global_settings_live.ex
+#, elixir-autogen, elixir-format
+msgid "No fields selected. Add at least the email field."
+msgstr ""
+
+#: lib/mv_web/live/global_settings_live.ex
+#, elixir-autogen, elixir-format
+msgid "Remove field %{label}"
+msgstr ""
+
+#: lib/mv_web/live/global_settings_live.ex
+#, elixir-autogen, elixir-format
+msgid "Board approval required (in development)"
+msgstr "Board approval required (in development)"
+
+#: lib/mv_web/live/global_settings_live.ex
+#, elixir-autogen, elixir-format
+msgid "Individual fields"
+msgstr "Individual fields"
+
+#: lib/mv_web/live/global_settings_live.ex
+#, elixir-autogen, elixir-format
+msgid "Personal data"
+msgstr "Personal data"
+
+#: lib/mv_web/components/core_components.ex
+#, elixir-autogen, elixir-format
+msgid "Reorder"
+msgstr "Reorder"
+
+#: lib/mv_web/live/global_settings_live.ex
+#, elixir-autogen, elixir-format
+msgid "The order of rows determines the field order in the join form."
+msgstr "The order of rows determines the field order in the join form."

priv/repo/migrations/20260310114701_add_join_form_settings_to_settings.exs

@@ -0,0 +1,27 @@
+defmodule Mv.Repo.Migrations.AddJoinFormSettingsToSettings do
+  @moduledoc """
+  Adds join form configuration columns to the settings table.
+
+  - join_form_enabled: whether the public /join page is active
+  - join_form_field_ids: ordered list of field IDs shown on the join form (JSONB array)
+  - join_form_field_required: map of field ID => required boolean (JSONB)
+  """
+
+  use Ecto.Migration
+
+  def up do
+    alter table(:settings) do
+      add :join_form_enabled, :boolean, default: false, null: false
+      add :join_form_field_ids, {:array, :string}
+      add :join_form_field_required, :map
+    end
+  end
+
+  def down do
+    alter table(:settings) do
+      remove :join_form_enabled
+      remove :join_form_field_ids
+      remove :join_form_field_required
+    end
+  end
+end

test/membership/setting_join_form_test.exs

@@ -0,0 +1,308 @@
+defmodule Mv.Membership.SettingJoinFormTest do
+  @moduledoc """
+  TDD tests for Join Form Settings (onboarding-join-concept subtask 3).
+
+  These tests define the expected API and behaviour for the "Onboarding / Join" section
+  in global settings. No functionality is implemented yet; tests are expected to fail
+  (red) until:
+
+  - Setting resource has attributes: `join_form_enabled`, `join_form_field_ids`,
+    `join_form_field_required`, plus validations and accept in the update action.
+  - `Mv.Membership.get_join_form_allowlist/0` is implemented and returns the allowlist
+    for the public join form (subtask 4).
+  """
+  # Settings is a singleton; tests mutate shared DB state. We use async: false and on_exit to restore
+  # original values because Ecto Sandbox transaction rollback does not apply to this singleton pattern.
+  use Mv.DataCase, async: false
+
+  alias Mv.Constants
+  alias Mv.Helpers.SystemActor
+  alias Mv.Membership
+
+  setup do
+    {:ok, settings} = Membership.get_settings()
+    saved_enabled = Map.get(settings, :join_form_enabled)
+    saved_ids = Map.get(settings, :join_form_field_ids)
+    saved_required = Map.get(settings, :join_form_field_required)
+
+    on_exit(fn ->
+      {:ok, s} = Membership.get_settings()
+      attrs = %{}
+
+      attrs =
+        if saved_enabled != nil,
+          do: Map.put(attrs, :join_form_enabled, saved_enabled),
+          else: attrs
+
+      attrs =
+        if saved_ids != nil,
+          do: Map.put(attrs, :join_form_field_ids, saved_ids || []),
+          else: attrs
+
+      attrs =
+        if saved_required != nil,
+          do: Map.put(attrs, :join_form_field_required, saved_required || %{}),
+          else: attrs
+
+      if attrs != %{} do
+        Membership.update_settings(s, attrs)
+      end
+    end)
+
+    :ok
+  end
+
+  defp update_join_form_settings(settings, attrs) do
+    Membership.update_settings(settings, attrs)
+  end
+
+  defp error_message(errors, field) when is_atom(field) do
+    errors
+    |> Enum.filter(fn err -> Map.get(err, :field) == field end)
+    |> Enum.map(&Map.get(&1, :message, ""))
+    |> List.first() || ""
+  end
+
+  # ---- 1. Persistence and loading ----
+
+  describe "join form settings persistence and loading" do
+    test "save and load join_form_enabled plus field selection and required flags returns same config" do
+      {:ok, settings} = Membership.get_settings()
+
+      attrs = %{
+        join_form_enabled: true,
+        join_form_field_ids: ["email", "first_name"],
+        join_form_field_required: %{"email" => true, "first_name" => false}
+      }
+
+      assert {:ok, updated} = update_join_form_settings(settings, attrs)
+      assert updated.join_form_enabled == true
+      assert updated.join_form_field_ids == ["email", "first_name"]
+      assert updated.join_form_field_required["email"] == true
+      assert updated.join_form_field_required["first_name"] == false
+
+      {:ok, reloaded} = Membership.get_settings()
+      assert reloaded.join_form_enabled == true
+      assert reloaded.join_form_field_ids == ["email", "first_name"]
+      assert reloaded.join_form_field_required["email"] == true
+      assert reloaded.join_form_field_required["first_name"] == false
+    end
+
+    test "repeated save with changed field list overwrites config without leftovers" do
+      {:ok, settings} = Membership.get_settings()
+
+      assert {:ok, _} =
+               update_join_form_settings(settings, %{
+                 join_form_enabled: true,
+                 join_form_field_ids: ["email", "first_name"],
+                 join_form_field_required: %{"email" => true, "first_name" => false}
+               })
+
+      assert {:ok, updated} =
+               update_join_form_settings(settings, %{
+                 join_form_enabled: true,
+                 join_form_field_ids: ["email", "last_name"],
+                 join_form_field_required: %{"email" => true, "last_name" => false}
+               })
+
+      assert updated.join_form_field_ids == ["email", "last_name"]
+      assert Map.has_key?(updated.join_form_field_required, "last_name")
+      refute Map.has_key?(updated.join_form_field_required, "first_name")
+    end
+  end
+
+  # ---- 2. Validation ----
+
+  describe "join form settings validation" do
+    test "only existing member fields or custom field ids are accepted; unknown field names rejected or sanitized" do
+      {:ok, settings} = Membership.get_settings()
+
+      result =
+        update_join_form_settings(settings, %{
+          join_form_enabled: true,
+          join_form_field_ids: ["email", "not_a_member_field"],
+          join_form_field_required: %{"email" => true, "not_a_member_field" => false}
+        })
+
+      # Until attributes exist we get NoSuchInput; once implemented we expect validation error
+      assert {:error, _} = result
+    end
+
+    test "config without email is rejected or email is auto-added and required" do
+      {:ok, settings} = Membership.get_settings()
+
+      result =
+        update_join_form_settings(settings, %{
+          join_form_enabled: true,
+          join_form_field_ids: ["first_name", "last_name"],
+          join_form_field_required: %{"first_name" => true, "last_name" => false}
+        })
+
+      # Either rejected or, when loaded, email must be present and required
+      case result do
+        {:error, _} ->
+          :ok
+
+        {:ok, updated} ->
+          assert "email" in updated.join_form_field_ids
+          assert updated.join_form_field_required["email"] == true
+      end
+    end
+
+    test "required false for email is ignored or forced to true when saved" do
+      {:ok, settings} = Membership.get_settings()
+
+      {:ok, updated} =
+        update_join_form_settings(settings, %{
+          join_form_enabled: true,
+          join_form_field_ids: ["email", "first_name"],
+          join_form_field_required: %{"email" => false, "first_name" => false}
+        })
+
+      assert updated.join_form_field_required["email"] == true
+    end
+
+    test "required flag for field not in join_form_field_ids is rejected or dropped" do
+      {:ok, settings} = Membership.get_settings()
+
+      result =
+        update_join_form_settings(settings, %{
+          join_form_enabled: true,
+          join_form_field_ids: ["email"],
+          join_form_field_required: %{"email" => true, "first_name" => true}
+        })
+
+      case result do
+        {:error, _} ->
+          :ok
+
+        {:ok, updated} ->
+          refute Map.has_key?(updated.join_form_field_required, "first_name")
+      end
+    end
+  end
+
+  # ---- 3. Allowlist for join form ----
+
+  describe "join form allowlist" do
+    test "allowlist returns configured fields with required/optional when join form enabled" do
+      {:ok, settings} = Membership.get_settings()
+
+      update_join_form_settings(settings, %{
+        join_form_enabled: true,
+        join_form_field_ids: ["email", "first_name"],
+        join_form_field_required: %{"email" => true, "first_name" => false}
+      })
+
+      allowlist = Membership.get_join_form_allowlist()
+
+      assert length(allowlist) == 2
+      email_entry = Enum.find(allowlist, &(&1.id == "email"))
+      first_name_entry = Enum.find(allowlist, &(&1.id == "first_name"))
+      assert email_entry.required == true
+      assert first_name_entry.required == false
+      assert email_entry.type == :member_field
+      assert first_name_entry.type == :member_field
+    end
+
+    test "allowlist returns empty or defined default when join form disabled" do
+      {:ok, settings} = Membership.get_settings()
+
+      update_join_form_settings(settings, %{
+        join_form_enabled: false,
+        join_form_field_ids: ["email", "first_name"],
+        join_form_field_required: %{"email" => true, "first_name" => false}
+      })
+
+      allowlist = Membership.get_join_form_allowlist()
+
+      assert allowlist == []
+    end
+
+    @tag :requires_custom_field
+    test "allowlist distinguishes member fields and custom field identifiers" do
+      {:ok, settings} = Membership.get_settings()
+      actor = SystemActor.get_system_actor()
+
+      {:ok, cf} =
+        Membership.create_custom_field(
+          %{name: "join_cf_#{System.unique_integer([:positive])}", value_type: :string},
+          actor: actor
+        )
+
+      update_join_form_settings(settings, %{
+        join_form_enabled: true,
+        join_form_field_ids: ["email", cf.id],
+        join_form_field_required: %{"email" => true, cf.id => false}
+      })
+
+      allowlist = Membership.get_join_form_allowlist()
+
+      email_entry = Enum.find(allowlist, &(&1.id == "email"))
+      cf_entry = Enum.find(allowlist, &(&1.id == cf.id))
+      assert email_entry.type == :member_field
+      assert cf_entry.type == :custom_field
+    end
+  end
+
+  # ---- 4. Defaults and fallback ----
+
+  describe "join form defaults and fallback" do
+    test "when no join settings stored, allowlist returns defined default (e.g. disabled, empty list)" do
+      allowlist = Membership.get_join_form_allowlist()
+      # Default: join form disabled → empty allowlist
+      assert is_list(allowlist)
+      assert allowlist == [] || Enum.all?(allowlist, &(is_map(&1) and Map.has_key?(&1, :id)))
+    end
+
+    test "existing settings without join keys load correctly; new join keys get defaults" do
+      {:ok, settings} = Membership.get_settings()
+      # Ensure other attributes still load
+      assert Map.has_key?(settings, :club_name)
+      # When join keys exist they have sensible defaults
+      join_enabled = Map.get(settings, :join_form_enabled)
+      join_ids = Map.get(settings, :join_form_field_ids)
+      if join_enabled != nil, do: assert(is_boolean(join_enabled))
+      if join_ids != nil, do: assert(is_list(join_ids))
+    end
+  end
+
+  # ---- 5. Authorization (backend: settings update requires authorized actor when policy enforced) ----
+  # Authorization for the settings page is covered by GlobalSettingsLive and page-permission tests.
+  # If the domain later requires an actor for update_settings, tests here would pass an actor.
+
+  # ---- 6. Robustness / edge cases ----
+
+  describe "join form settings robustness" do
+    test "invalid or unexpected payload structure yields clean error or ignores unknown keys" do
+      {:ok, settings} = Membership.get_settings()
+
+      result =
+        update_join_form_settings(settings, %{
+          join_form_enabled: true,
+          join_form_field_ids: "not_a_list",
+          join_form_field_required: %{}
+        })
+
+      assert match?({:error, _}, result) or
+               (match?({:ok, _}, result) && elem(result, 1).join_form_field_ids != "not_a_list")
+    end
+
+    test "larger but reasonable number of fields saves and loads without error" do
+      {:ok, settings} = Membership.get_settings()
+      all_member = Constants.member_fields() |> Enum.map(&to_string/1)
+      required_map = Map.new(all_member, fn f -> {f, f == "email"} end)
+
+      assert {:ok, updated} =
+               update_join_form_settings(settings, %{
+                 join_form_enabled: true,
+                 join_form_field_ids: all_member,
+                 join_form_field_required: required_map
+               })
+
+      assert length(updated.join_form_field_ids) == length(all_member)
+      {:ok, reloaded} = Membership.get_settings()
+      assert length(reloaded.join_form_field_ids) == length(all_member)
+    end
+  end
+end