fix: extract member_id from relationship changes during validation (#168)

lib/mv/accounts/user/validations/email_not_used_by_other_member.ex

@@ -41,18 +41,37 @@ defmodule Mv.Accounts.User.Validations.EmailNotUsedByOtherMember do
     if should_validate? do
       case Ash.Changeset.fetch_change(changeset, :email) do
         {:ok, new_email} ->
-          check_email_uniqueness(new_email, member_id)
+          # Extract member_id from relationship changes for new links
+          member_id_to_exclude = get_member_id_from_changeset(changeset)
+          check_email_uniqueness(new_email, member_id_to_exclude)
 
         :error ->
           # No email change, get current email
           current_email = Ash.Changeset.get_attribute(changeset, :email)
-          check_email_uniqueness(current_email, member_id)
+          # Extract member_id from relationship changes for new links
+          member_id_to_exclude = get_member_id_from_changeset(changeset)
+          check_email_uniqueness(current_email, member_id_to_exclude)
       end
     else
       :ok
     end
   end
 
+  # Extract member_id from changeset, checking relationship changes first
+  # This is crucial for new links where member_id is in manage_relationship changes
+  defp get_member_id_from_changeset(changeset) do
+    # Try to get from relationships (for new links via manage_relationship)
+    case Map.get(changeset.relationships, :member) do
+      [{[%{id: id}], _opts}] when not is_nil(id) ->
+        # Found in relationships - this is a new link
+        id
+
+      _ ->
+        # Fall back to attribute (for existing links)
+        Ash.Changeset.get_attribute(changeset, :member_id)
+    end
+  end
+
   defp check_email_uniqueness(email, exclude_member_id) do
     query =
       Mv.Membership.Member