any option to use expressions also in headers array of a stream. So a JSON payload would have some values, which can be grabbed (e.g. via expressions) and put inside of header data? See below a try to utilize expression for uuid.
{
  "protocol_id": 7,
  "enabled": true,
  "validate_message": "",
  "name": "OTA_functionCallResult",
  "configuration": {
    "headers": [
      {
        "name": "Authorization",
        "value": "xyz"
      },
      {
        "name": "X-Metadata",
        "value": "taskName=OFC_Result",
         "value": "uuid=%2+3%"    
      }
    ],
    "ident": "%ident%",
    "limit_messages": 100,
    "uri": "https://xyz"
  },
  "queue_ttl": 86400,
  "metadata": {}
}