Enrolment plugins are nicely de-coupled from course settings, except Guest Access.

Proposal:
Have a Settings page as part of the Guest Access enrolment method which contains the 2 fields currently in Course Settings. Furthermore, allow multiple instances of the method.

Rationale:
+ all enrolment plugins should be consistent in terms of handling and management
+ enrolment and course method should be de-coupled
+ multiple enrolment instances should be allowed, if feasible

Optional / nice to have:
+ custom instance name
+ validity limited by date range