curl --request PATCH \
  --url https://sandbox-api.prava.space/v1/carts/{cart_id} \
  --header 'Api-Key: <api-key>' \
  --header 'Content-Type: application/json' \
  --data '{
  "add": [
    {
      "product_id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
      "qty": 123
    }
  ],
  "remove": [
    "3c90c3cc-0d44-4b50-8888-8dd25736052a"
  ]
}'

{
  "data": {
    "cart_id": "c1b2a3d4-e5f6-7890-1234-567890abcdef",
    "customer_id": "d290f1ee-6c54-4b01-90e6-d701748f0851",
    "merchant_id": "m1e2r3c4-h5a6-n7t8-9012-3456789abcde",
    "status": "open",
    "created_at": "2025-10-15T05:36:43.000Z",
    "updated_at": "2025-10-15T05:38:00.000Z"
  },
  "meta": {
    "request_id": "req_12345",
    "timestamp": "2025-10-15T05:38:00.000Z",
    "idempotency_key": "ee461e0f-1808-4018-9ee1-2744a8e822f7"
  }
}