public function sendVerificationLink(CanVerifyEmailContract $user, Closure $callback = null)
    {
        // Once we have the verify token, we are ready to send the message out to this
        // user with a link to verify their email. We will then redirect back to
        // the current URI having nothing set in the session to indicate errors.
        $token = $this->tokens->create($user);

        $this->emailVerificationLink($user, $token, $callback);

        return VerifyEmailBrokerContract::VERIFY_LINK_SENT;
    }