Slack rate limits

[maxwofford]

We're getting rate-limited hard by slack & usability goes down when more than 50 active hack hours are running at the same time.

I'd like to setup a message queue for anything that's not 100% critical & send the message out with logic to prevent us getting ratelimited like this

[techpixel]

doesn't bolt already have a message queue? I also want to cut down on unnecessary messages (eg. logs)