Prepare all types objects before serialising

Activities returned from inbox can include other types of objects like
Article

test/support/factory.ex

@@ -57,6 +57,11 @@ defmodule Pleroma.Factory do
     %Pleroma.Object{data: Map.merge(data, %{"to" => [user2.ap_id]})}
   end
 
+  def article_factory do
+    note_factory()
+    |> Map.put("type", "Article")
+  end
+
   def tombstone_factory do
     data = %{
       "type" => "Tombstone",
@@ -110,6 +115,26 @@ defmodule Pleroma.Factory do
     }
   end
 
+  def article_activity_factory do
+    article = insert(:article)
+
+    data = %{
+      "id" => Pleroma.Web.ActivityPub.Utils.generate_activity_id(),
+      "type" => "Create",
+      "actor" => article.data["actor"],
+      "to" => article.data["to"],
+      "object" => article.data,
+      "published" => DateTime.utc_now() |> DateTime.to_iso8601(),
+      "context" => article.data["context"]
+    }
+
+    %Pleroma.Activity{
+      data: data,
+      actor: data["actor"],
+      recipients: data["to"]
+    }
+  end
+
   def announce_activity_factory do
     note_activity = insert(:note_activity)
     user = insert(:user)