onNativeVoicePush method
Register a sink for incoming-call payloads delivered natively (iOS APNs VoIP/PushKit). On Android the equivalent arrives as an FCM data message handled in Dart, so this never fires there.
Implementation
@override
void onNativeVoicePush(void Function(Map<String, dynamic> data) sink) {
_voicePushSink = sink;
final p = _pendingVoicePush;
if (p != null) {
_pendingVoicePush = null;
sink(p);
}
}