Improved jwt logic

* No longer stores full token, but only payload.

src/Broker/TopicManager.php

@@ -69,7 +69,7 @@ class TopicManager
                     'topic' => $topic->getTopic(),
                     'subscriber' => $sub->getId(),
                     'active' => true,
-                    'payload' => null, // TODO populate from mercure.payload in JWT
+                    'payload' => $sub->getPayload(),
                 ];
             }
         }