Handles push notifications from pub sub for the cloud-builds topic.
Google Cloud Build will automatically publish these messages for all cloud builds.
Note that GCP does not publish this message for manual running gcloud builds submit.
But manually running a cloud build trigger with gcloud beta builds triggers run <trigger> will cause cloud build to publish pub sub messages with build statuses.
The forward-service collects additional build info from GCP cloud build api and publishes a new pub sub message to the ciccd-builds topic.