Changes to POST `/api/v0/main-frontend/course-credit-registrations/registrations/{credit_registration_id}/recheck-enrolment` - Asks the pipeline to look for an enrolment again, for a row parked because the study registry had none. Shares the student's limit on asking, so between them they cannot start more than one check in 30 minutes. Authorized on the row's own course, like the retry.