title: Square API: Create Checkout API error
body: <p>When using the sample POSTMAN request:</p>
  
  <pre><code>{
    "idempotency_key": "74ae1696-b1e3-4328-af6d-f1e04d947a13",
    "order": {
      "reference_id": "my-order-001",
      "line_items": [
      {
        "name": "line-item-1",
        "quantity": "1",
        "base_price_money": {
          "amount": 1599,
          "currency": "USD"
        }
      },
      {
        "name": "line-item-2",
        "quantity": "2",
        "base_price_money": {
          "amount": 799,
          "currency": "USD"
        }
      }]
    },
    "ask_for_shipping_address": true,
    "merchant_support_email": "merchant+support@website.com",
    "pre_populate_buyer_email": "buyer@email.com",
    "pre_populate_shipping_address": {
      "address_line_1": "500 Electric Ave",
      "address_line_2": "Suite 600",
      "locality": "New York",
      "administrative_district_level_1": "NY",
      "postal_code": "10003",
      "first_name": "Jane",
      "last_name": "Doe"
    },
    "redirect_url": "https://merchant.website.com/order-confirm"
  }
  </code></pre>
  
  <p>I'm getting the following response:</p>
  
  <pre><code>{
    "errors": [
      {
        "category": "INVALID_REQUEST_ERROR",
        "code": "INVALID_VALUE",
        "detail": "The order must have at least one line item.",
          "field": "line_items"
      }]
  }
  </code></pre>
  
  <p>This is simply executing the sample POSTMAN requests available via <a href="https://docs.connect.squareup.com/api/connect/v2/#runningpostman" rel="nofollow noreferrer">https://docs.connect.squareup.com/api/connect/v2/#runningpostman</a></p>