Add the after_initialize configuration hook

[rsamoilov]

Description

Currently, Rage lacks support for the after_initialize hook that allows to defer running a block of code to after the application has been initialised. Adding this hook would allow users to configure the application and reference application-level constants.

Example:

Rage.config.after_initialize do
  Rollbar.configure do |config|
    config.ignored_person_ids = User.test_users.ids
  end
end

Tips

• See the description of the hook in Rails Guides.
• Check the overview doc that shows how Rage's core components interact with each other.
• Feel free to ask any questions or request help in the comments below!