Manage pulse credentials centrally

[djmitche]

Problem

We currently configure pulse credentials in each of our services manually - creating a new user in pulseguardian and manually adding the username / password to the service configuration.

Proposal

Handle pulse credentials the same way we do AWS, Azure, Sentry, and Statsum credentials: services use TC credentials to request temporary pulse credentials.

This is a little more complicated than those other services, though:

• rabbitmq does not permit credential expiration, so we must expire things manually
• we need to terminate running connections on expiration
• we need to delete queues on expiration
• the pulseguardian-implied correspndance of usernames to queue/exchange names is different
• need to monitor queue length
• ..other things

Implementation

Tracker: https://bugzilla.mozilla.org/show_bug.cgi?id=1436456

[djmitche]

We decided at the SF all-hands to stop pursuing this particular project right now.