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>

lib/federation/activity_pub/fetcher.ex

@@ -142,7 +142,7 @@ defmodule Mobilizon.Federation.ActivityPub.Fetcher do
       true
     else
       Sentry.capture_message("Object origin check failed", extra: %{url: url, data: data})
-      Logger.debug("Object origin check failed")
+      Logger.debug("Object origin check failed between #{inspect(url)} and #{inspect(data)}")
       false
     end
   end

lib/federation/activity_pub/utils.ex

@@ -239,6 +239,8 @@ defmodule Mobilizon.Federation.ActivityPub.Utils do
 
   Takes the actor or attributedTo attributes (considers only the first elem if they're an array)
   """
+  def origin_check?(id, %{"type" => "Tombstone", "id" => tombstone_id}), do: id == tombstone_id
+
   def origin_check?(id, %{"actor" => actor, "attributedTo" => _attributed_to} = params)
       when not is_nil(actor) and actor != "" do
     params = Map.delete(params, "attributedTo")