Add product by id handler

src/Imprink.Application/Commands/Products/GetProductById.cs

@@ -1,6 +1,51 @@
+using Imprink.Application.Dtos;
+using MediatR;
+
 namespace Imprink.Application.Commands.Products;
 
-public class GetProductById
+public class GetProductByIdQuery : IRequest<ProductDto?>
 {
-    
+    public Guid ProductId { get; set; }
+}
+
+public class GetProductById(
+    IUnitOfWork unitOfWork) 
+    : IRequestHandler<GetProductByIdQuery, ProductDto?>
+{
+    public async Task<ProductDto?> Handle(
+        GetProductByIdQuery request, 
+        CancellationToken cancellationToken)
+    {
+        var product = await unitOfWork.ProductRepository
+            .GetByIdAsync(request.ProductId, cancellationToken);
+        
+        if (product == null)
+            return null;
+
+        return new ProductDto
+        {
+            Id = product.Id,
+            Name = product.Name,
+            Description = product.Description,
+            BasePrice = product.BasePrice,
+            IsCustomizable = product.IsCustomizable,
+            IsActive = product.IsActive,
+            ImageUrl = product.ImageUrl,
+            CategoryId = product.CategoryId,
+            Category = new CategoryDto
+            {
+                Id = product.Category.Id,
+                Name = product.Category.Name,
+                Description = product.Category.Description,
+                ImageUrl = product.Category.ImageUrl,
+                SortOrder = product.Category.SortOrder,
+                IsActive = product.Category.IsActive,
+                ParentCategoryId = product.Category.ParentCategoryId,
+                CreatedAt = product.Category.CreatedAt,
+                ModifiedAt = product.Category.ModifiedAt
+            },
+            CreatedAt = product.CreatedAt,
+            ModifiedAt = product.ModifiedAt
+        };
+    }
 }