showNotification method
Shows a notification with the specified title, body and payload.
If title is null, the title will default to 'Message from {sender_name}'.
If body is null, the body will default to the message.
Implementation
Future<void> showNotification({
String? title,
String? body,
required Map<String, dynamic> payload,
}) {
throw UnimplementedError(
'setNotificationHandler() has not been implemented.');
}