delete method
Deletes a property, or a whole device when property is null, and
tells connected clients.
Implementation
void delete(String device, [String? property]) {
_definitions.removeWhere(
(key, _) => key.$1 == device && (property == null || key.$2 == property),
);
for (final connection in connections) {
if (connection._wants(device, property)) {
connection.send(DelProperty(device: device, name: property));
}
}
}