private function isUserConflict(EzUser $user, TokenInterface $previousToken = null)
    {
        if ($previousToken === null || !$previousToken instanceof UsernamePasswordToken) {
            return false;
        }

        $previousUser = $previousToken->getUser();
        if (!$previousUser instanceof EzUser) {
            return false;
        }

        $wasAnonymous = $previousUser->getAPIUser()->getUserId() == $this->configResolver->getParameter('anonymous_user_id');
        // TODO: isEqualTo is not on the interface
        return !$wasAnonymous && !$user->isEqualTo($previousUser);
    }