Add migration for DiscountProductImages table

- Created a new table `DiscountProductImages` in the CMS schema.
- Added columns for image details including `Title`, `AltText`, `ImagePath`, `ThumbnailPath`, `SortOrder`, `IsActive`, `Created`, `CreatedBy`, `LastModified`, `LastModifiedBy`, and `IsDeleted`.
- Established a foreign key relationship with the `DiscountProducts` table.
- Created indexes on `DiscountProductId` and a composite index on `DiscountProductId` and `SortOrder`.

src/CMSMicroservice.Application/Common/Interfaces/IApplicationDbContext.cs

@@ -51,6 +51,7 @@ public interface IApplicationDbContext
     DbSet<DiscountProduct> DiscountProducts { get; }
     DbSet<DiscountCategory> DiscountCategories { get; }
     DbSet<DiscountProductCategory> DiscountProductCategories { get; }
+    DbSet<DiscountProductImage> DiscountProductImages { get; }
     DbSet<DiscountShoppingCart> DiscountShoppingCarts { get; }
     DbSet<DiscountOrder> DiscountOrders { get; }
     DbSet<DiscountOrderDetail> DiscountOrderDetails { get; }

src/CMSMicroservice.Application/Common/Services/VatCalculator.cs

@@ -0,0 +1,83 @@
+namespace CMSMicroservice.Application.Common.Services;
+
+/// <summary>
+/// سرویس محاسبه مالیات بر ارزش افزوده (VAT)
+/// </summary>
+public static class VatCalculator
+{
+    /// <summary>
+    /// نرخ VAT ایران - 9 درصد
+    /// </summary>
+    public const decimal VAT_RATE = 0.09m;
+    
+    /// <summary>
+    /// نرخ VAT به صورت درصد (9)
+    /// </summary>
+    public const int VAT_PERCENT = 9;
+
+    /// <summary>
+    /// محاسبه VAT از مبلغ خالص
+    /// </summary>
+    /// <param name="netAmount">مبلغ خالص (بدون مالیات)</param>
+    /// <returns>مبلغ VAT</returns>
+    public static long CalculateVat(long netAmount)
+    {
+        return (long)(netAmount * VAT_RATE);
+    }
+
+    /// <summary>
+    /// محاسبه مبلغ ناخالص (شامل VAT) از مبلغ خالص
+    /// </summary>
+    /// <param name="netAmount">مبلغ خالص</param>
+    /// <returns>مبلغ ناخالص (خالص + VAT)</returns>
+    public static long CalculateGrossAmount(long netAmount)
+    {
+        return netAmount + CalculateVat(netAmount);
+    }
+
+    /// <summary>
+    /// استخراج مبلغ خالص از مبلغ ناخالص
+    /// </summary>
+    /// <param name="grossAmount">مبلغ ناخالص (شامل VAT)</param>
+    /// <returns>مبلغ خالص</returns>
+    public static long ExtractNetAmount(long grossAmount)
+    {
+        return (long)(grossAmount / (1 + VAT_RATE));
+    }
+
+    /// <summary>
+    /// استخراج VAT از مبلغ ناخالص
+    /// </summary>
+    /// <param name="grossAmount">مبلغ ناخالص (شامل VAT)</param>
+    /// <returns>مبلغ VAT</returns>
+    public static long ExtractVatFromGross(long grossAmount)
+    {
+        return grossAmount - ExtractNetAmount(grossAmount);
+    }
+
+    /// <summary>
+    /// جزئیات محاسبه VAT
+    /// </summary>
+    public record VatBreakdown(
+        long NetAmount,
+        long VatAmount,
+        long GrossAmount,
+        decimal VatRate
+    );
+
+    /// <summary>
+    /// محاسبه کامل جزئیات VAT
+    /// </summary>
+    /// <param name="netAmount">مبلغ خالص</param>
+    /// <returns>جزئیات کامل VAT</returns>
+    public static VatBreakdown CalculateBreakdown(long netAmount)
+    {
+        var vatAmount = CalculateVat(netAmount);
+        return new VatBreakdown(
+            NetAmount: netAmount,
+            VatAmount: vatAmount,
+            GrossAmount: netAmount + vatAmount,
+            VatRate: VAT_RATE
+        );
+    }
+}