def set_callbacks_on_some_models
      ShinyNewsletters::Template.set_callback :create, :after, :add_elements
      ShinyNewsletters::Edition.set_callback  :create, :after, :add_elements
      ShinyPages::Template.set_callback       :create, :after, :add_elements
      ShinyPages::Page.set_callback           :create, :after, :add_elements