feat: Implement Discount Product and Shopping Cart functionalities

- Added UpdateDiscountProductCommandValidator for validating discount product updates.
- Created GetDiscountProductByIdQuery and its handler for retrieving discount product details by ID.
- Implemented GetDiscountProductsQuery and handler for fetching a list of discount products with filtering options.
- Developed AddToCartCommand and handler for adding products to the shopping cart.
- Implemented ClearCartCommand and handler for clearing the shopping cart.
- Created RemoveFromCartCommand and handler for removing items from the cart.
- Added UpdateCartItemCountCommand and handler for updating the quantity of items in the cart.
- Developed GetUserCartQuery and handler for retrieving the user's shopping cart details.
- Implemented Product Tag functionalities including assigning tags to products, creating, updating, and deleting tags.
- Added queries for fetching all tags and products by tag.

src/BackOffice.BFF.Application/DiscountOrderCQ/Commands/PlaceOrder/PlaceOrderCommand.cs

@@ -0,0 +1,16 @@
+namespace BackOffice.BFF.Application.DiscountOrderCQ.Commands.PlaceOrder;
+
+public record PlaceOrderCommand : IRequest<PlaceOrderResponseDto>
+{
+    /// <summary>شناسه کاربر</summary>
+    public long UserId { get; init; }
+    
+    /// <summary>شناسه آدرس ارسال</summary>
+    public long AddressId { get; init; }
+    
+    /// <summary>مبلغ پرداخت از موجودی تخفیف</summary>
+    public long DiscountBalanceAmount { get; init; }
+    
+    /// <summary>مبلغ پرداخت از درگاه</summary>
+    public long GatewayAmount { get; init; }
+}