curl --request POST \
  --url https://api.sprucecollective.co.uk/api/merch/checkout \
  --header 'Content-Type: application/json' \
  --data '
{
  "address_line1": "<string>",
  "country_code": "<string>",
  "items": [
    {
      "assets": [
        {}
      ],
      "copies": 2,
      "sku": "<string>",
      "attributes": {},
      "sizing": "<string>"
    }
  ],
  "postal_or_zip_code": "<string>",
  "recipient_name": "<string>",
  "shipping_method": "Budget",
  "site_id": "<string>",
  "town_or_city": "<string>",
  "address_line2": "<string>",
  "checkout_id": "<string>",
  "recipient_email": "<string>",
  "recipient_phone": "<string>",
  "state_or_county": "<string>"
}
'

{
  "checkout_id": "<string>",
  "order_id": "<string>"
}