Add validators and services for Product Galleries and Product Tags

- Implemented Create, Delete, Get, and Update validators for Product Galleries.
- Added Create, Delete, Get, and Update validators for Product Tags.
- Created service classes for handling Discount Categories, Discount Orders, Discount Products, Discount Shopping Cart, Product Categories, Product Galleries, and Product Tags.
- Each service class integrates with CQRS for command and query handling.
- Established mapping profiles for Product Galleries.

src/CMSMicroservice.Domain/Entities/ProductGallery.cs

@@ -0,0 +1,11 @@
+namespace CMSMicroservice.Domain.Entities;
+//گالری تصاویر محصول
+public class ProductGallery : BaseAuditableEntity
+{
+    public long ProductImageId { get; set; }
+    //ProductImage Navigation Property
+    public virtual ProductImage ProductImage { get; set; }
+    public long ProductId { get; set; }
+    //Product Navigation Property
+    public virtual Product Product { get; set; }
+}