Cop Idea: Limit Controller Custom Actions

[mollerhoj]

Limiting public controller actions to the 7 standard actions prevents fat controllers and generally enforces better domain modeling, as demonstrated in this talk https://www.youtube.com/watch?v=HctYHe-YjnE
and this blog post: http://jeromedalbert.com/how-dhh-organizes-his-rails-controllers/

I would like to see a rubocop that enforces that the 7 standard actions are only public methods in controllers.

This will work nicely with #547

I'm a bit confused about how to proceed. I'm not sure that my suggestion is being accepted in the style guide, though the discussion is ongoing: (rubocop/rails-style-guide#290). Is that a prerequisite for the cop to be accepted?

If I get a go from a core member, I'd love to do a PR for this cop

[koic]

#827 is proposed as an implementation. However, the style guide is currently under discussion:
rubocop/rails-style-guide#290