CompositeFirebaseEventTrackerFactory
class CompositeFirebaseEventTrackerFactory(factories: List<FirebaseEventTrackerFactory>) : FirebaseEventTrackerFactory(source)
Asks each factory in order and takes the first answer that is not a decline.
Order decides the configuration: put your own factory first to override how a marker is handled, and end with GenericFirebaseEventTrackerFactory if every event should reach Firebase somehow. Leave that terminator out and an unclaimed event is simply not tracked.