The endpoint receives events from BigBlueButton via webhooks or scripts
in the record and playback workflow.
For now it only treats the event for when a recording is ready.
When it happens, it uses action cable to update the interface dynamically
with the new recording.
Unlisted is a state between published and unpublished. They are still
published in the server, but will not appear to anyone other than the
user that created the recording.
It is done using a metadata attribute and required several changes in how
the application handles publishing and unpublishing.
