* 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
Also removes the remove_course_goal method as it is no longer
used anywhere and removes the functionality of deleting course goals
if a user unenrolls. Adds in fields for eventing to make them more
useful.
* fix type mismatch in course_goals migrations
* fix type mismatch in experiments migrations
* fix type mismatch in xblock_django migrations
* fix type mismatch in catalog migrations
* fix type mismatch in static_replace migrations
* fix type mismatch in bulk_email migrations
* fix type mismatch in course_overviews migrations
Django 2.0 will make this field required for `ForeignKey` and `OneToOneFields`.
In previous versions the option defaulted to `models.CASCADE` when not
specified. This change should make the deprecation warnings in the current
Django version go away.
The migrations where also modified, but the changes should not cause a change in
the database schema since `models.CASCADE` was already the old default.
LEARNER-2308
Once a goal has been set for a user on the course home message,
allow them to update it on the course home side bar. Automatically
sets a course goal for users when enrolling in a verifiable course.
