reject method
Implementation
@override
Future<void> reject({RejectReason reason = RejectReason.declined}) async {
_set(ringing: false);
final result = await _module.signalWithRetry('rtc.reject', '$_path/reject', {'call_id': callId, 'reason': reason.name});
final call = asMap(result['call']);
if (call != null) applyCall(call);
}