curl --request POST \
  --url https://api.headlesscommerce.io/v1/admin/orders/{id}/complete \
  --header 'Authorization: Bearer <token>'

{
  "id": "<string>",
  "number": 123,
  "status": "draft",
  "payment_status": "unpaid",
  "fulfillment_status": "unfulfilled",
  "customer_id": "<string>",
  "email": "<string>",
  "shipping_address": {
    "name": "<string>",
    "company": "<string>",
    "line1": "<string>",
    "line2": "<string>",
    "city": "<string>",
    "state": "<string>",
    "postal_code": "<string>",
    "country": "<string>",
    "phone": "<string>"
  },
  "billing_address": {
    "name": "<string>",
    "company": "<string>",
    "line1": "<string>",
    "line2": "<string>",
    "city": "<string>",
    "state": "<string>",
    "postal_code": "<string>",
    "country": "<string>",
    "phone": "<string>"
  },
  "lines": [
    {
      "id": "<string>",
      "variant_id": "<string>",
      "product_id": "<string>",
      "product_name": "<string>",
      "variant_name": "<string>",
      "sku": "<string>",
      "image_url": "<string>",
      "quantity": 123,
      "unit_price": {
        "amount": 123,
        "currency": "<string>"
      },
      "line_discount": {
        "amount": 123,
        "currency": "<string>"
      },
      "line_total": {
        "amount": 123,
        "currency": "<string>"
      },
      "tax_amount": {
        "amount": 123,
        "currency": "<string>"
      },
      "fulfilled_quantity": 123,
      "refunded_quantity": 123
    }
  ],
  "subtotal": {
    "amount": 123,
    "currency": "<string>"
  },
  "discount_total": {
    "amount": 123,
    "currency": "<string>"
  },
  "shipping_total": {
    "amount": 123,
    "currency": "<string>"
  },
  "tax_total": {
    "amount": 123,
    "currency": "<string>"
  },
  "total": {
    "amount": 123,
    "currency": "<string>"
  },
  "refunded_total": {
    "amount": 123,
    "currency": "<string>"
  },
  "applied_discounts": [
    {
      "discount_id": "<string>",
      "code": "<string>",
      "name": "<string>",
      "value_type": "fixed",
      "value": 123,
      "saved": {
        "amount": 123,
        "currency": "<string>"
      }
    }
  ],
  "shipping_method_name": "<string>",
  "note": "<string>",
  "payments": [
    {
      "id": "<string>",
      "order_id": "<string>",
      "provider": "<string>",
      "provider_id": "<string>",
      "amount": {
        "amount": 123,
        "currency": "<string>"
      },
      "status": "pending",
      "created_at": "2023-11-07T05:31:56Z"
    }
  ],
  "fulfillments": [
    {
      "id": "<string>",
      "order_id": "<string>",
      "status": "pending",
      "tracking_number": "<string>",
      "tracking_url": "<string>",
      "carrier": "<string>",
      "lines": [
        {
          "order_line_id": "<string>",
          "quantity": 123
        }
      ],
      "created_at": "2023-11-07T05:31:56Z",
      "shipped_at": "2023-11-07T05:31:56Z",
      "delivered_at": "2023-11-07T05:31:56Z"
    }
  ],
  "refunds": [
    {
      "id": "<string>",
      "order_id": "<string>",
      "amount": {
        "amount": 123,
        "currency": "<string>"
      },
      "reason": "<string>",
      "restock": true,
      "status": "pending",
      "lines": [
        {
          "order_line_id": "<string>",
          "quantity": 123
        }
      ],
      "created_at": "2023-11-07T05:31:56Z"
    }
  ],
  "metadata": {},
  "created_at": "2023-11-07T05:31:56Z",
  "cancelled_at": "2023-11-07T05:31:56Z",
  "completed_at": "2023-11-07T05:31:56Z"
}