onRegStateChanged method
Handles registtation state changes when received response from server
Implementation
void onRegStateChanged(int accId, RegState state, String response) {
_logs?.print('onRegStateChanged accId:$accId resp:\'$response\' ${state.toString()}');
AccountModel? acc = _findAccount(accId);
if(acc == null) return;
acc.regText = response;
acc.regState = state;
notifyListeners();
}