Remove native oauth feature

[davidor]

This is a feature that has been deprecated for a long time.
@andreumasferrer gave us the 👍 to delete this.

[unleashed]

The helpers in the listener code and the required params missing error might have been only used by the code removed, but they aren't specific to OAuth tokens and look generic enough that they could be used elsewhere. Maybe there's an opportunity to start using them?

[davidor]

I don't see how those methods can be reused.

require_params! can't be reused because it raises a generic error whereas the rest of methods in the Listener class raise specific errors such as ServiceIdMissing.
ensure_authenticated! is not needed in the rest of the methods of the class.