Make Active Storage routes optional

[gmcgibbon]

Summary

Currently, I don't see a way of turning off Active Storage's default routes. They are drawn on the host application and not on the engine (due to direct and resolve being used). For applications that only want to use assets internally, or need to point to different controllers to meet their app's needs, the only way to remove routes currently is something like this:

initializer(:remove_activestorage_routes, after: :add_routing_paths) do |app|
  app.routes_reloader.paths.delete_if { |path| path =~ /activestorage/ }
end

Does it make sense to make this easier? cc @georgeclaghorn

[gmcgibbon]

Looks like CI is complaining about my development config bleeding into other tests. I'll see if I can fix that

The default value was nil so routes weren't being drawn by default. 🤦‍♂