Refactor Doorkeeper::Rails::Helpers
Refactor Doorkeeper::Rails::Helpers

Makes explicit what the public API is to inject doorkeeper behavior into
application endpoints.

This should be the only interface between Rails and doorkeeper. Other
frameworks can define their own interface and use doorkeeper too. This
is a step into decoupling doorkeeper from Rails, so that integration
is easier.

Related with https://github.com/doorkeeper-gem/doorkeeper/pull/567.

AdStage/doorkeeper,stefania11/doorkeeper,pmdeazeta/doorkeeper,AICIDNN/doorkeeper,daande/doorkeeper,GeekOnCoffee/doorkeeper,dollarshaveclub/doorkeeper,jasl/doorkeeper,vanboom/doorkeeper,ngpestelos/doorkeeper,dk1234567/doorkeeper,ukasiu/doorkeeper,nbulaj/doorkeeper,doorkeeper-gem/doorkeeper,telekomatrix/doorkeeper,ezilocchi/doorkeeper,mavenlink/doorkeeper,identification-io/doorkeeper,lalithr95/doorkeeper,vovimayhem/doorkeeper,doorkeeper-gem/doorkeeper,EasterAndJay/doorkeeper,calfzhou/doorkeeper,stefania11/doorkeeper,outstand/doorkeeper,AICIDNN/doorkeeper,ukasiu/doorkeeper,ValMilkevich/doorkeeper,stormz/doorkeeper,kolorahl/doorkeeper,calfzhou/doorkeeper,Uysim/doorkeeper,identification-io/doorkeeper,pmdeazeta/doorkeeper,AdStage/doorkeeper,outstand/doorkeeper,telekomatrix/doorkeeper,moneytree/doorkeeper,Uysim/doorkeeper,vanboom/doorkeeper,mavenlink/doorkeeper,6fusion/doorkeeper,mavenlink/doorkeeper,dk1234567/doorkeeper,GeekOnCoffee/doorkeeper,kolorahl/doorkeeper,daande/doorkeeper,ValMilkevich/doorkeeper,dollarshaveclub/doorkeeper,ezilocchi/doorkeeper,jasl/doorkeeper,EasterAndJay/doorkeeper,vovimayhem/doorkeeper,lalithr95/doorkeeper,moneytree/doorkeeper,doorkeeper-gem/doorkeeper,stormz/doorkeeper,6fusion/doorkeeper,jasl/doorkeeper,outstand/doorkeeper,nbulaj/doorkeeper,ngpestelos/doorkeeper