delete method
Deletes a record.
Return true
if record was deleted or false
if record does not exists
Throws AssertionError if uuid is null or empty.
Implementation
Future<bool> delete() async {
_checkId();
var deleted = await storeRef.record(uuid!).delete(await database);
_controller.add(this as T);
_controller.close();
return deleted == null ? false : true;
}