refactor: integrate approval ui review changes

lib/membership/join_request/changes/helpers.ex

@@ -0,0 +1,19 @@
+defmodule Mv.Membership.JoinRequest.Changes.Helpers do
+  @moduledoc """
+  Shared helpers for JoinRequest change modules (e.g. ApproveRequest, RejectRequest).
+  """
+
+  @doc """
+  Extracts the actor's user id from the Ash change context.
+
+  Supports both atom and string keys for compatibility with different actor representations.
+  """
+  @spec actor_id(term()) :: String.t() | nil
+  def actor_id(nil), do: nil
+
+  def actor_id(actor) when is_map(actor) do
+    Map.get(actor, :id) || Map.get(actor, "id")
+  end
+
+  def actor_id(_), do: nil
+end