PubSub editor role required to use notifications

[jonblack]

When PubSub notifications are enabled and the registry-events topic already exists in the given project, the registry server fails to startup with the following error:

FATAL[0001] Failed to create registry server error=rpc error: code = PermissionDenied desc = User not authorized to perform this action.

Due to organizational rules, it's not possible to give the service account the required roles/pubsub.editor role (the topic is created via internal tooling).

This line tries to create the topic and will fail gracefully if it already exists. I'm assuming that due to lack of permissions, it bails out instead.