Move hidden fields from view to pre_authorization, for supporting other parameters.

[takada-s]

Currently, authorizations/new view has hardwired hidden_field_tags, used to pass parameters, such as scope and state, between authN and authZ.

I also trying to support OpenID Connect on this Doorkeeper, so I want to pass a new parameter nonce.
Using my changes, we can easily pass the new parameter and can avoid overriding/repeating code.

[houndci-bot]

Use 2 spaces for indentation in a hash, relative to the start of the line where the left curly brace is.

[tute]

With this change you'd need to override/monkey patch Doorkeeper::OAuth::PreAuthorization#hidden_fields. It would be easier to override the view, using the standard Rails practice of recreating the view tree in the app folder. Doorkeeper has a generator for this:

$ rails g doorkeeper:views
      create  app/views/doorkeeper/applications
      create  app/views/doorkeeper/applications/_delete_form.html.erb
      create  app/views/doorkeeper/applications/_form.html.erb
      create  app/views/doorkeeper/applications/edit.html.erb
      create  app/views/doorkeeper/applications/index.html.erb
      create  app/views/doorkeeper/applications/new.html.erb
      ...

Closing for now, willing to continue discussion for sure. Thank you for your work and willing to share!

[toupeira]

@tute follow-up to my comment in #897: I've now implemented nonces in doorkeeper-openid_connect by extending certain Doorkeeper classes (switching to prepend so I can use super).

So since I'm already monkey-patching, the current solution in this PR seems acceptable to me, and I think overriding the view would only make things more complicated for end-users of my gem. Would you be willing to merge this as is?