Display MQTT 5 CONNECT User Property in Management UI

[ansd]

Display MQTT 5 CONNECT User Property in Management UI and CLI as requested in #2554 (comment)

[v5 3.1.2.11.8]

User Properties on the CONNECT packet can be used to send connection related properties from the Client to the Server. The meaning of these properties is not defined by this specification.

It makes sense to display the User Property of the CONNECT packet in the Management UI in the connection's Client Properties.

Example:

mqttx conn --client-id client-1 --user-properties "name 1: value 1" --user-properties "name 2: value 2"
mqttx conn --client-id client-2

CLI output:

rabbitmqctl list_mqtt_connections client_id conn_name user_property --formatter=json | jq .
[
  {
    "client_id": "client-2",
    "conn_name": "127.0.0.1:21898 -> 127.0.0.1:1883",
    "user_property": []
  },
  {
    "client_id": "client-1",
    "conn_name": "127.0.0.1:21826 -> 127.0.0.1:1883",
    "user_property": [
      [
        "name 1",
        "value 1"
      ],
      [
        "name 2",
        "value 2"
      ]
    ]
  }
]

Management UI:

[michaelklishin]

@ansd since they are user-provided, we must ensure that they are properly HTML-escaped. Otherwise it would be a great XSS exploit vector.

[ansd]

@michaelklishin they are HTML-escaped.