curl -X POST https://api.open.cx/connect/threads/order_84421/participants \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{ "role": "courier", "external_id": "drv_318",
        "display_name": "Aleksei", "language": "en" }'

{
  "participant": { "id": "prt_d55", "role": "courier", "external_id": "drv_318",
                   "display_name": "Aleksei", "language": "en" },
  "lanes": [
    { "id": "customer_merchant", "status": "active" },
    { "id": "customer_courier", "status": "active" }
  ]
}