- Add new 'missedmessage_email_senders' queue for sending missed messages emails.
- Add the new worker to process 'missedmessage_email_senders' queue.
- Split aggregation missed messages and sending missed messages email
to separate queue workers.
- Adapt tests for sending missed emails to the new logic.
Fixes#2607
The previous model for these Nagios checks was kinda crazy -- every
minute, we'd run a full `rabbitmctl list_consumers` for each of the
dozen+ consumers that we have, and then do the exact same parsing
logic for each to determine whether the target queue has a running
consumer to write out a state file.
Because `rabbitmctl list_consumers` takes a small amount of resources,
on systems where CPU is very limited (e.g. t2 style AWS instances),
this minor CPU wastage could be problematic.
Now we just do that `rabbitmqctl list_consumers` once per minute, and
output all the state files from a single command.
Further TODO items on this front include removing the hardcoded list
of queues.