For the dates courseware tab, we no longer respect the
course_home_use_legacy_frontend waffle flag that enabled the
legacy version in Maple.
Instead, we always send the user to the MFE.
MFEs will be required for the Nutmeg release. This dates tab is
the first to fall, but others will follow.
AA-799
* Add unsubscribe_token uuid field to CourseGoal model
* Add endpoint to unsubcribe from just a token (no login needed)
* Add admin page for the course_goals djangoapp
* Add get_course_overview_or_404 utility method
* Clean up URL handling in course_home_api
AA-907