Vereinfacht client: find by email in response, no retries in test

API does not allow filter[email]; fetch list and match client-side.
Disable Req retries in test for fast failure and less log noise.

lib/mv/vereinfacht/client.ex

@@ -42,15 +42,18 @@ defmodule Mv.Vereinfacht.Client do
     end
   end
 
+  @sync_timeout_ms 5_000
+
+  # In test, skip retries so sync fails fast when no API is running (avoids log spam and long waits).
+  defp req_http_options do
+    opts = [receive_timeout: @sync_timeout_ms]
+    if Mix.env() == :test, do: [retry: false] ++ opts, else: opts
+  end
+
   defp post_and_parse_contact(url, body, api_key) do
-    # Req expects body to be iodata (e.g. string); a raw map causes ArgumentError.
     encoded_body = Jason.encode!(body)
 
-    case Req.post(url,
-           body: encoded_body,
-           headers: headers(api_key),
-           receive_timeout: 15_000
-         ) do
+    case Req.post(url, [body: encoded_body, headers: headers(api_key)] ++ req_http_options()) do
       {:ok, %{status: 201, body: resp_body}} ->
         case get_contact_id_from_response(resp_body) do
           nil -> {:error, {:invalid_response, resp_body}}
@@ -95,10 +98,12 @@ defmodule Mv.Vereinfacht.Client do
         |> String.trim_trailing("/")
         |> then(&"#{&1}/finance-contacts/#{contact_id}")
 
-      case Req.patch(url,
-             body: encoded_body,
-             headers: headers(api_key),
-             receive_timeout: 15_000
+      case Req.patch(
+             url,
+             [
+               body: encoded_body,
+               headers: headers(api_key)
+             ] ++ req_http_options()
            ) do
         {:ok, %{status: 200, body: _resp_body}} ->
           {:ok, contact_id}
@@ -112,6 +117,73 @@ defmodule Mv.Vereinfacht.Client do
     end
   end
 
+  @doc """
+  Finds a finance contact by email (GET /finance-contacts, then match in response).
+
+  The Vereinfacht API does not allow filter by email on this endpoint, so we
+  fetch the first page and find the contact client-side. Returns {:ok, contact_id}
+  if a contact with that email exists, {:error, :not_found} if none, or
+  {:error, reason} on API/network failure. Used before create for idempotency.
+  """
+  @spec find_contact_by_email(String.t()) :: {:ok, String.t()} | {:error, :not_found | term()}
+  def find_contact_by_email(email) when is_binary(email) do
+    if is_nil(base_url()) or is_nil(api_key()) or is_nil(club_id()) do
+      {:error, :not_configured}
+    else
+      do_find_contact_by_email(email)
+    end
+  end
+
+  defp do_find_contact_by_email(email) do
+    url =
+      base_url()
+      |> String.trim_trailing("/")
+      |> then(&"#{&1}/finance-contacts")
+
+    case Req.get(url, [headers: headers(api_key())] ++ req_http_options()) do
+      {:ok, %{status: 200, body: body}} when is_map(body) ->
+        parse_find_by_email_response(body, email)
+
+      {:ok, %{status: status, body: body}} ->
+        {:error, {:http, status, extract_error_message(body)}}
+
+      {:error, reason} ->
+        {:error, {:request_failed, reason}}
+    end
+  end
+
+  defp parse_find_by_email_response(body, email) do
+    normalized = String.trim(email) |> String.downcase()
+
+    case find_contact_id_by_email_in_list(body, normalized) do
+      nil -> {:error, :not_found}
+      id -> {:ok, id}
+    end
+  end
+
+  defp find_contact_id_by_email_in_list(%{"data" => list}, normalized) when is_list(list) do
+    Enum.find_value(list, fn
+      %{"id" => id, "attributes" => %{"email" => att_email}} when is_binary(att_email) ->
+        if att_email |> String.trim() |> String.downcase() == normalized do
+          normalize_contact_id(id)
+        else
+          nil
+        end
+
+      %{"id" => _id, "attributes" => _} ->
+        nil
+
+      _ ->
+        nil
+    end)
+  end
+
+  defp find_contact_id_by_email_in_list(_, _), do: nil
+
+  defp normalize_contact_id(id) when is_binary(id), do: id
+  defp normalize_contact_id(id) when is_integer(id), do: to_string(id)
+  defp normalize_contact_id(_), do: nil
+
   @doc """
   Fetches a single finance contact from Vereinfacht (GET /finance-contacts/:id).
 
@@ -130,10 +202,7 @@ defmodule Mv.Vereinfacht.Client do
         |> String.trim_trailing("/")
         |> then(&"#{&1}/finance-contacts/#{contact_id}")
 
-      case Req.get(url,
-             headers: headers(api_key),
-             receive_timeout: 15_000
-           ) do
+      case Req.get(url, [headers: headers(api_key)] ++ req_http_options()) do
         {:ok, %{status: 200, body: body}} when is_map(body) ->
           {:ok, body}