oneWithID<T> method
Checks if a document exists in the RDB using its type and ID.
Implementation
Future<bool> oneWithID<T>(Type type, String documentID, { String? subcollection }) async {
String path = RDB.constructPathForClassAndID(type, documentID, subcollection: subcollection);
final snapshot = await RDB.instance.ref(path).get();
return snapshot.exists;
}