Create a new "StationQueue" entity that contains the upcoming song queue, and split the important AutoDJ functionality across multiple classes (Annotations, Queue and Scheduler).
- Switch to EntityManagerInterface for EM uses
- Wrap EntityManager in close-resilient wrapper
- Close/clear/reopen EM with every request
- Rework tests to be em->clear() resilient.
* Commit new Schedule entity changes and new API endpoints.
* Fix possible cause of API POST errors.
* Fix syntax with JSON return slashes.
* Add "Schedule View" and "Enforce Schedule" settings to Streamers.
* Add "Scheduled" panel to Profile.