Feature request: being able to completely disable push notifications

[tvdijen]

I can't use push notifications for several irrelevant reasons, but the code assumes that this should be possible and will try to send them anyway.
This currently leads to an error being displayed to the users stating that push notification failed.

It would be nice to be able to skip the entire push-notification code, either based on a feature flag, or maybe even better, implicitly when the required config (cert or key) is missing/set to null.