Follow up of https://tracker.moodle.org/browse/MOBILE-3150
The Firebase SDK gets a push token/ push id/ however you call it directly after the first launch of the App if the Google Play Services are installed. This indicates that the App/ Firebase SDK registers at Google.
This is a privacy issue.
It is possible to disable this auto registration, see https://firebase.google.com/docs/cloud-messaging/android/client#prevent-auto-init