feat(business): add support for fetching order details

[salman0ansari]

• added function GetOrderDetails to fetch order details
• a new business.go file is introduced to house this and other business-related logic.
• data structures for the order details are defined in types/business.go.

Usage

// you can get order id and token from the OrderMessage
orderDetails, err := client.GetOrderDetails(context.Background(), "order-id-here", "order-token-here")
if err != nil {
    // handle error
}
fmt.Printf("Order %s has %d products\n", orderDetails.ID, len(orderDetails.Products))

Response

{
  "id": "order-id-here",
  "created_at": "YYYY-MM-DDTHH:MM:SS+TZ",
  "catalog_id": "catalog-id-here",
  "price": {
    "subtotal": 1,
    "total": 1,
    "currency": "USD",
    "price_status": "provided"
  },
  "products": [
    {
      "id": "product-id-here",
      "image_id": "image-id-here",
      "image_url": "https://example.com/product-image.jpg",
      "price": 1,
      "currency": "USD",
      "name": "Product Name",
      "quantity": 1,
      "variant_info": {}
    }
  ]
}

[hrizal]

nice ...

[Diden05]

@tulir merge?