curl --request POST \
  --url 'https://api.example.com/api/cart/add' \
  --header 'x-widget-token: YOUR_API_KEY' \
  --header 'Content-Type: application/json' \
  --data '{
  "variantId": "string",
  "quantity": 1,
  "sessionId": "string"
}'

{
  "checkoutUrl": "string"
}