Use prompt=login outside of an oidc request

[jeffsawatzky]

The prompt=login etc is a nice feature to have even for non OIDC requests. Is there a reason why you restrict it to OIDC requests only?

[toupeira]

@jeffsawatzky well mainly because this gem is hooking into Doorkeeper internals and tries its best not to interfere with non-OIDC requests 😉

I would be fine with a PR to add a configuration option for this though, I don't think any of the prompt values depend on an actual OIDC request so we could have just one flag to enable all prompt parameter handling for non-OIDC requests.