Add utility functions for objects and activities.

test/object_test.exs

@@ -0,0 +1,11 @@
+defmodule Pleroma.ObjectTest do
+  use Pleroma.DataCase
+  import Pleroma.Factory
+
+  test "returns an object by it's AP id" do
+    object = insert(:note)
+    found_object = Pleroma.Object.get_by_ap_id(object.data["id"])
+
+    assert object == found_object
+  end
+end