add action changes for email sync

lib/mv/accounts/user/changes/sync_email_to_member.ex

@@ -0,0 +1,55 @@
+defmodule Mv.Accounts.User.Changes.SyncEmailToMember do
+  @moduledoc """
+  Synchronizes user email changes to the linked member.
+
+  When a user's email is updated and the user is linked to a member,
+  this change automatically updates the member's email to match.
+
+  This ensures bidirectional email synchronization with User.email
+  as the source of truth.
+
+  Uses `around_transaction` to guarantee atomicity - both the user
+  and member updates happen in the SAME database transaction.
+  """
+  use Ash.Resource.Change
+  alias Mv.EmailSync.Helpers
+
+  @impl true
+  def change(changeset, _opts, context) do
+    cond do
+      # Skip if already syncing to avoid recursion
+      Map.get(context, :syncing_email, false) ->
+        changeset
+
+      # Only proceed if email is actually changing
+      not Ash.Changeset.changing_attribute?(changeset, :email) ->
+        changeset
+
+      # Apply the sync logic
+      true ->
+        new_email = Ash.Changeset.get_attribute(changeset, :email)
+
+        # around_transaction receives the changeset (cs) from Ash
+        # and a callback that executes the actual database operation
+        Ash.Changeset.around_transaction(changeset, fn cs, callback ->
+          result = callback.(cs)
+
+          with {:ok, user} <- Helpers.extract_record(result),
+               linked_member <- get_linked_member(user) do
+            Helpers.sync_email_to_linked_record(result, linked_member, new_email)
+          else
+            _ -> result
+          end
+        end)
+    end
+  end
+
+  defp get_linked_member(%{member_id: nil}), do: nil
+
+  defp get_linked_member(%{member_id: member_id}) do
+    case Ash.get(Mv.Membership.Member, member_id) do
+      {:ok, member} -> member
+      {:error, _} -> nil
+    end
+  end
+end