Fix checking origin from a tombstone

When comparing an activity with their origin, only compare the ID
directly, as Tombstones don't have actors anymore

Signed-off-by: Thomas Citharel <tcit@tcit.fr>

test/federation/activity_pub/utils_test.exs

@@ -5,6 +5,7 @@ defmodule Mobilizon.Federation.ActivityPub.UtilsTest do
 
   import Mobilizon.Factory
 
+  alias Mobilizon.Federation.ActivityPub.Utils
   alias Mobilizon.Federation.ActivityStream.Converter
 
   alias Mobilizon.Web.Endpoint
@@ -51,4 +52,13 @@ defmodule Mobilizon.Federation.ActivityPub.UtilsTest do
       assert comment_data["inReplyTo"] == comment.url
     end
   end
+
+  describe "origin_check?" do
+    test "origin_check? with a tombstone" do
+      assert Utils.origin_check?("http://an_uri", %{
+               "type" => "Tombstone",
+               "id" => "http://an_uri"
+             })
+    end
+  end
 end