title: Allow one concurrent user per login with JWT
body: <p>We are developing an application with Laravel/PHP and we want to use an pay-per-user pricing model. For that we have to ensure that an account can only used by only one concurrent user. We use JWT for authentication and it is stateless so I can't use sessions.</p>
  <p>To ensure one concurrent login I can enclose the Browser-agent or IP, but both aren't unique and it is possible that they occur multiple times in e.g. an office. Also I can send the MAC address, but that is not the easiest way.</p>
  <p>Are there other solutions to ensure one concurrent login per user with JWT?</p>