/**
  * Class contructor
  * @param var $usr
  * @param var $sessionVar
  */
 public function __construct(UserManagement $um, Config $config, $dbInstanceKey = null)
 {
     parent::__construct($um, $config, $dbInstanceKey);
     $this->authYubikey = new Yubikey($config->yubico_id, $config->yubico_key);
 }