public function sendConfirmationEmail(FormEvent $event)
    {
        /** @var UserInterface $user */
        $user = $event->getForm()->getData();

        $user->setEnabled(false);
        if (null === $user->getConfirmationToken()) {
            $user->setConfirmationToken($this->generateToken());
        }

        $this->mailer->sendConfirmationEmailMessage($user);

        $this->session->set('silex_user_confirmation_email', $user->getEmail());

        $event->setResponse(new RedirectResponse($this->router->generate('silex_user.registration_check_email')));
    }