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()}');
int idx = _accounts.indexWhere((account) => (account.myAccId == accId));
if(idx == -1) return;
AccountModel acc = _accounts[idx];
acc.regText = response;
acc.regState = state;
notifyListeners();
}