useCallKit method
Advanced override — replace the built-in native call UI.
Implementation
void useCallKit(NexusCallKit callKit) {
final previous = _callKit;
if (previous is NexusNativeCallKit) previous.dispose();
_callKit = callKit;
_callKitSub?.cancel();
_callKitSub = _callKit.actions.listen(_onCallKitAction);
}