Add resctriction only admin could delete topic

lib/diskuy_web/controllers/topic_controller.ex

@@ -40,8 +40,9 @@ defmodule DiskuyWeb.TopicController do
 
   def delete(conn, %{"id" => id}) do
     topic = Forum.get_topic_by_name!(id)
-
-    with {:ok, %Topic{}} <- Forum.delete_topic(topic) do
+    current_user = Guardian.Plug.current_resource(conn)
+    with {:ok, :authorized} <- Guardian.check_admin(current_user),
+         {:ok, %Topic{}} <- Forum.delete_topic(topic) do
       send_resp(conn, :no_content, "")
     end
   end