curl --request PUT \
  --url {protocol}://{host}/wp-json/cocart/preview/checkout \
  --header 'Content-Type: application/json' \
  --data '{
  "billing_address": {
    "first_name": "<string>",
    "last_name": "<string>",
    "company": "<string>",
    "address_1": "<string>",
    "address_2": "<string>",
    "city": "<string>",
    "state": "<string>",
    "postcode": "<string>",
    "country": "<string>",
    "phone": "<string>",
    "email": "jsmith@example.com"
  },
  "shipping_address": {
    "first_name": "<string>",
    "last_name": "<string>",
    "company": "<string>",
    "address_1": "<string>",
    "address_2": "<string>",
    "city": "<string>",
    "state": "<string>",
    "postcode": "<string>",
    "country": "<string>"
  },
  "payment_method": "<string>",
  "shipping_method": "<string>"
}'

{
  "cart_key": "abc123def456",
  "cart_hash": "d41d8cd98f00b204e9800998ecf8427e",
  "customer_id": 123,
  "billing_address": {
    "first_name": "John",
    "last_name": "Doe",
    "email": "john@example.com",
    "phone": "+1234567890",
    "address_1": "123 Main St",
    "address_2": "Apt 4B",
    "city": "Anytown",
    "state": "CA",
    "postcode": "12345",
    "country": "US",
    "company": ""
  },
  "shipping_address": {
    "first_name": "John",
    "last_name": "Doe",
    "address_1": "123 Main St",
    "address_2": "Apt 4B",
    "city": "Anytown",
    "state": "CA",
    "postcode": "12345",
    "country": "US",
    "company": ""
  },
  "cart_contents": {
    "c4ca4238a0b923820dcc509a6f75849b": {
      "key": "c4ca4238a0b923820dcc509a6f75849b",
      "product_id": 456,
      "variation_id": 0,
      "quantity": 2,
      "product_name": "Premium T-Shirt",
      "product_title": "Premium T-Shirt",
      "product_price": "$19.99",
      "line_total": "39.98",
      "line_subtotal": "39.98"
    }
  },
  "cart_totals": {
    "subtotal": "39.98",
    "subtotal_tax": "0.00",
    "shipping_total": "5.00",
    "shipping_tax": "0.00",
    "discount_total": "0.00",
    "discount_tax": "0.00",
    "cart_contents_total": "39.98",
    "cart_contents_tax": "0.00",
    "fee_total": "0.00",
    "fee_tax": "0.00",
    "total": "44.98",
    "total_tax": "0.00"
  },
  "shipping_methods": {
    "flat_rate:1": {
      "id": "flat_rate:1",
      "label": "Flat Rate",
      "cost": "5.00",
      "method_id": "flat_rate",
      "instance_id": "1"
    }
  },
  "needs_payment": true,
  "needs_shipping": true,
  "payment_method": "stripe"
}