ZEVA2 - set up a queue system service

Set up a queue system service, analogous to the "workers" service in ITVR and the "workers" service in CTHUB (they both use django-q).

Use BullMQ (https://docs.bullmq.io/); it is dependent on Redis. We can use this task queue service to send emails in a way such that if an email fails to send, we'll have knowledge of that and can resend (automatically or otherwise). There may be other uses as well.