title: Token based authentication for MQTT Broker
body: <p>I want to implement a token based Authentication mechanism for clients of a MQTT broker. </p>
  
  <p>I must have client token provisioning as a separate service, then in the <code>CONNECT</code> message sent from the client, I intend to include the token. </p>
  
  <p>Then ideally the broker should authenticate from the identity/token provider and send the <code>CONNACK</code>accordingly. </p>
  
  <ol>
  <li>I have considered <code>mosquitto</code> , <code>RabbitMQ</code> and <code>MOSCA</code> so far. What would be the ideal broker for the scenario above? </li>
  <li>Are there any loopholes or improvements to the scenario I described? </li>
  </ol>