persist qos2 and qos3 subscription to disk, default to false;
Source
bool get qosPersistenceEnabled {
if (dslinkJson is Map && dslinkJson['configs'] is Map && dslinkJson['configs']['qosPersistenceEnabled'] is Map
&& dslinkJson['configs']['qosPersistenceEnabled']['value'] == true) {
return true;
}
return false;
}