Progress

app/serializers/rest/list_serializer.rb

@@ -1,9 +1,10 @@
 # frozen_string_literal: true
 
 class REST::ListSerializer < ActiveModel::Serializer
-  attributes :id, :title
+  attributes :id, :title, :created_at
 
   def id
     object.id.to_s
   end
+
 end