How to scale the sentry slack integration

[kitsunde]

We have a whole bunch of AWS lambda projects and currently they push into a single sentry project, which has some drawbacks, and I'm looking into if I can split these up into individual sentry projects.

It seems like we can auto setup sentry projects via #23.

However, how can we turn on the slack integration across projects? It seems like it's configured on an individual project basis and with specific rules that seem quite tedious to setup for each project.