------------------
* Add `update_course_enrollment_mode_for_user` method to the EnrollmentApiClient.
* Create new API endpoint to update the mode for a user's licensed enterprise course enrollments when their enterprise license is revoked.
* Introduce new course run status for `saved_for_later`.
* On revocation of an enterprise license, mark the user's licensed course enrollments as `saved_for_later` and `is_revoked`.