Pub/Sub service

[lacarvalho91]

Summary

Add support for Pub/Sub as a notifications service.

Motivation

We use Pub/Sub heavily for other things, there are resiliency benefits using a Google managed service like Pub/Sub. Putting these notifications on a messaging service like Pub/Sub would allow many consumers of this data.

Proposal

Write a Pub/Sub implementation of the notifications service interface . It should also support using the Pub/Sub emulator for testing purposes.

I attempted to integrate with Pub/Sub using a webhook service. However I got stuck because GCP doesn't support long lived access tokens so it doesn't seem possible.

[KyriosGN0]

i'll take a go at it