curl --request PUT \
  --url 'https://prod-api.stateset.cloud.stateset.app/api/v1/checkout/{session_id}/customer' \
  --header 'Authorization: Bearer YOUR_API_KEY' \
  --header 'Content-Type: application/json' \
  --data '{
  "email": "ada.lovelace@example.com",
  "subscribe_newsletter": true
}'

{
  "data": {
    "billing_address": {
      "address_line_1": "548 Market St",
      "address_line_2": "Suite 400",
      "city": "San Francisco",
      "company": "Acme Outdoors",
      "country_code": "US",
      "first_name": "Ada",
      "last_name": "Lovelace",
      "phone": "+1 415 555 0142",
      "postal_code": "94107",
      "province": "CA"
    },
    "cart_id": "3fa85f64-5717-4562-b3fc-2c963f66afa6",
    "currency": "USD",
    "customer_email": "ada.lovelace@example.com",
    "id": "3fa85f64-5717-4562-b3fc-2c963f66afa6",
    "payment_method": "CreditCard",
    "shipping_address": {
      "address_line_1": "548 Market St",
      "address_line_2": "Suite 400",
      "city": "San Francisco",
      "company": "Acme Outdoors",
      "country_code": "US",
      "first_name": "Ada",
      "last_name": "Lovelace",
      "phone": "+1 415 555 0142",
      "postal_code": "94107",
      "province": "CA"
    },
    "shipping_method": "Standard",
    "step": "string",
    "subtotal": "49.00",
    "total": "49.00"
  },
  "errors": [
    "string"
  ],
  "message": "Two-person tent, green — replacement for damaged pole set.",
  "meta": {
    "request_id": "3fa85f64-5717-4562-b3fc-2c963f66afa6",
    "timestamp": "2026-08-31T14:22:05Z"
  },
  "success": true
}