watchAll method
Watch all items, emitting a new list on any change.
The includeInitialData parameter controls whether the stream should
immediately emit the current list of all items. Defaults to true.
If false, the stream will only emit when a change occurs.
Return null if the adapter doesn't support reactive queries.
Implementation
Stream<List<T>>? watchAll({String? userId, bool includeInitialData = true}) => null;