curl --request PUT \
  --url https://api.getsly.ai/v1/v1/ucp/checkouts/{id} \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "merchant_id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
  "items": [
    {
      "sku": "<string>",
      "quantity": 123,
      "unit_price": "<string>",
      "currency": "<string>",
      "description": "<string>"
    }
  ],
  "currency": "USD",
  "style": "modal",
  "success_url": "<string>",
  "cancel_url": "<string>",
  "expires_in": 900,
  "metadata": {}
}
'

{
  "data": {
    "id": "<string>",
    "merchant_id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
    "items": [
      {
        "sku": "<string>",
        "quantity": 123,
        "unit_price": "<string>",
        "currency": "<string>",
        "description": "<string>"
      }
    ],
    "total": "<string>",
    "currency": "<string>",
    "expires_at": "2023-11-07T05:31:56Z",
    "created_at": "2023-11-07T05:31:56Z",
    "session_url": "<string>",
    "success_url": "<string>",
    "cancel_url": "<string>",
    "metadata": {}
  }
}