Add code for verifying homeservers' signatures on API requests

lib/matrix_server_web/federation/key_controller.ex

@@ -9,7 +9,7 @@ defmodule MatrixServerWeb.Federation.KeyController do
 
   def get_signing_keys(conn, _params) do
     keys =
-      SigningServer.get_signing_keys()
+      SigningServer.get_signing_keys(true)
       |> Enum.into(%{}, fn {key_id, key} ->
         {key_id, %{"key" => key}}
       end)

lib/matrix_server_web/federation/test_controller.ex

@@ -0,0 +1,10 @@
+defmodule MatrixServerWeb.Federation.TestController do
+  use MatrixServerWeb, :controller
+  use MatrixServerWeb.AuthenticateServer
+
+  def test(conn, _params) do
+    conn
+    |> put_status(200)
+    |> json(%{})
+  end
+end