Voice providers
Which voice services the app can use right now. A service that runs out of credit or stops answering is put on hold and tested again every 30 minutes; use Test now after topping it up.
Normal order
Channels without their own order below try these in turn. Set in Railway (TTS_PROVIDER, TTS_FALLBACK_PROVIDER).
Channel voices
Give a channel its own order of voice services. It then uses only the services switched on, in that order, and if none of them can voice it the job waits and carries on by itself when one is back. Channels left on the normal order use every backup.
Priority channels
New jobs from these channels go to the front of the queue, behind any other priority jobs. The job being voiced is never interrupted. Switching a channel on also moves its waiting jobs up.
Storage
A finished voiceover's audio and its parts are deleted this many days after they were made. Jobs that are queued, being voiced, paused or waiting are never touched. Re-voicing reuses the saved parts, so after this point a re-run voices the whole video again.