Route helpers are not available within ActiveAdmin views, even root_path is not available in the context of view Class.

ActionController::UrlGenerationError - No route matches {:action=>"index", :controller=>"active_admin/users"}:
  app/views/active_admin/_sidebar.html.erb:3
  app/views/layouts/active_admin.html.erb:15

It seems to be related to the recent change of separating contexts, so these helpers are still available under main_app variable.

Expected behavior

Route helpers are available.

Actual behavior

Helpers are not available, ActiveAdmin v4 code throws exception for new and generated resource.

How to reproduce

• initialise ActiveAdmin v4 project
• generate sample resource
• run the app, try accessing the resource