Transmogrifier: Don't modify attachments for chats.

lib/pleroma/web/activity_pub/transmogrifier.ex

@@ -1114,6 +1114,9 @@ def add_attributed_to(object) do
     Map.put(object, "attributedTo", attributed_to)
   end
 
+  # TODO: Revisit this
+  def prepare_attachments(%{"type" => "ChatMessage"} = object), do: object
+
   def prepare_attachments(object) do
     attachments =
       object

test/web/common_api/common_api_test.exs

@@ -54,6 +54,8 @@ test "it posts a chat message" do
 
       assert Chat.get(author.id, recipient.ap_id)
       assert Chat.get(recipient.id, author.ap_id)
+
+      assert :ok == Pleroma.Web.Federator.perform(:publish, activity)
     end
 
     test "it reject messages over the local limit" do