[WIP] Add taskcluster pulse support.

[tomprince]

This enables listening to taskcluster pulse messages, and triggering jenkins to pull from taskcluster.

This depends on mozilla-releng/scriptworker#371 and https://github.com/mozilla-services/cloudops-infra-deploylib/pull/99

[tomprince]

The job triggering definitely needs fleshing out, and it may be that this should be a separate service. It doesn't need to be publicly accessible, as it connects to outbound to pulse to listen.

[sciurus]

I'm guessing there is no generic functionality in taskcluster to generate a webhook when a certain event happens (i.e. like github or dockerhub webhooks)? Thus the need to hook the deployment proxy into pulse, or build a new service that listens to pulse and generates webhooks to the deployment proxy?

[tomprince]

There isn't currently a generic webhook functionality in taskcluster. We could have a docker-worker task that calls an http endpoint, but if we wanted to authenticate that call, we'd need to store some sort of credentials for it in taskcluster, which this set of PRs is working to move away from needing to do.

[oremj]

Looks like this setting isn't used anywhere.

[tomprince]

It should be passed to the pulse connection. I wrote this a while ago, but I suspect I wanted to use an anonymous queue for testing locally.

[oremj]

Can you document what route will look like?

[tomprince]

I've added my initial thoughts on what this would look like here.

[tomprince]

(rebased on #22)

[oremj]

Closing in favor of #22