Load the nested models of eager loaded models

[jcmfernandes]

Generated nested models register themselves upon being created by Avromatic::Model::Builder. If Rails's autoloader didn't recreate a model that should be eager loaded, then its nested models won't be registered as we hook on Railtie #to_prepare that itself triggers a clean-up of the nested models registry.

Therefore, we have to go through the attribute definitions of each eager loaded model and try to register its nested models.

prime @jturkel

[jcmfernandes]

Hey @jturkel, I did some changes based on your feedback. Let me know what you think. Thanks!

[jcmfernandes]

Alright, all done! 😉