Configuration method for prompt=select_account about doorkeeper-openid_connect

[linhdangduy]

@toupeira Thank for your attention. I'm happy to propose a PR!

[toupeira]

@linhdangduy that's a great question, I don't remember what I had in mind when I originally wrote this 😅

But yes I think adding configuration for this makes sense! 👍

In the default proc we could raise Errors::InvalidConfiguration as the others do, and get rid of Errors::AccountSelectionRequired.

Do you want to submit a PR?

[toupeira]

@linhdangduy oh and BTW there's potential for name clashes in Doorkeeper::OpenidConnect::Helpers::Controller because it's included in other controllers, so I propose we call the method there something like select_account_for_oidc_resource_owner and the configuration value maybe select_account_for_resource_owner, receiving the owner as only argument? Happy with other names too, just the method in the helper should include oidc somewhere.