Improve Federation boundaries

lib/mobilizon_web/auth/error_handler.ex

@@ -0,0 +1,11 @@
+defmodule MobilizonWeb.Auth.ErrorHandler do
+  @moduledoc """
+  In case we have an auth error
+  """
+  import Plug.Conn
+
+  def auth_error(conn, {type, _reason}, _opts) do
+    body = Jason.encode!(%{message: to_string(type)})
+    send_resp(conn, 401, body)
+  end
+end