public function onAuthenticationSuccess(AuthenticationEvent $event)
    {
        if (!$this->config['admin_login']) {
            return;
        }

        $token = $event->getAuthenticationToken();
        $userIsAdmin = $this->accessDecisionManager->decide($token, ['ROLE_ADMIN']);

        // Only for Admins and fully authenticated
        if (!($userIsAdmin && $token instanceof UsernamePasswordToken)) {
            return;
        }

        /** @var \Ekyna\Bundle\UserBundle\Model\UserInterface $user */
        $user = $token->getUser();

        $this->mailer->sendSuccessfulLoginEmailMessage($user);
    }