curl -X POST \
 /checkout-links/{id}/cart \
 --header "Content-Type: application/json" \
 --header "Authorization: Bearer <token>" \
 --data '{
    "customerId": "ad7f7b7d-7b7d-7b7d-7b7d-7b7d-7b7d7b7d7b7d",
    "metadata": [
        ""
    ]
}'

{
  "cartId": "ad7f7b7d-7b7d-7b7d-7b7d-7b7d7b7d7b7d",
  "customerId": "ad7f7b7d-7b7d-7b7d-7b7d-7b7d7b7d7b7d",
  "url": "https://example.com/cart/123"
}