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.Protobuf/Protos/discountcategory.proto

@@ -0,0 +1,100 @@
+syntax = "proto3";
+
+package discountcategory;
+
+import "public_messages.proto";
+import "google/protobuf/empty.proto";
+import "google/protobuf/wrappers.proto";
+import "google/protobuf/timestamp.proto";
+import "google/api/annotations.proto";
+
+option csharp_namespace = "CMSMicroservice.Protobuf.Protos.DiscountCategory";
+
+service DiscountCategoryContract
+{
+    rpc CreateDiscountCategory(CreateDiscountCategoryRequest) returns (CreateDiscountCategoryResponse){
+        option (google.api.http) = {
+            post: "/CreateDiscountCategory"
+            body: "*"
+        };
+    };
+    rpc UpdateDiscountCategory(UpdateDiscountCategoryRequest) returns (google.protobuf.Empty){
+        option (google.api.http) = {
+            put: "/UpdateDiscountCategory"
+            body: "*"
+        };
+    };
+    rpc DeleteDiscountCategory(DeleteDiscountCategoryRequest) returns (google.protobuf.Empty){
+        option (google.api.http) = {
+            delete: "/DeleteDiscountCategory"
+            body: "*"
+        };
+    };
+    rpc GetDiscountCategories(GetDiscountCategoriesRequest) returns (GetDiscountCategoriesResponse){
+        option (google.api.http) = {
+            get: "/GetDiscountCategories"
+        };
+    };
+}
+
+// Create Category
+message CreateDiscountCategoryRequest
+{
+    string name = 1;
+    string title = 2;
+    google.protobuf.StringValue description = 3;
+    google.protobuf.StringValue image_path = 4;
+    google.protobuf.Int64Value parent_category_id = 5;
+    int32 sort_order = 6;
+    bool is_active = 7;
+}
+
+message CreateDiscountCategoryResponse
+{
+    int64 category_id = 1;
+}
+
+// Update Category
+message UpdateDiscountCategoryRequest
+{
+    int64 category_id = 1;
+    string name = 2;
+    string title = 3;
+    google.protobuf.StringValue description = 4;
+    google.protobuf.StringValue image_path = 5;
+    google.protobuf.Int64Value parent_category_id = 6;
+    int32 sort_order = 7;
+    bool is_active = 8;
+}
+
+// Delete Category
+message DeleteDiscountCategoryRequest
+{
+    int64 category_id = 1;
+}
+
+// Get Categories with Tree Structure
+message GetDiscountCategoriesRequest
+{
+    google.protobuf.Int64Value parent_category_id = 1; // null = root categories
+    google.protobuf.BoolValue is_active = 2;
+}
+
+message GetDiscountCategoriesResponse
+{
+    repeated DiscountCategoryDto categories = 1;
+}
+
+message DiscountCategoryDto
+{
+    int64 id = 1;
+    string name = 2;
+    string title = 3;
+    google.protobuf.StringValue description = 4;
+    google.protobuf.StringValue image_path = 5;
+    google.protobuf.Int64Value parent_category_id = 6;
+    int32 sort_order = 7;
+    bool is_active = 8;
+    int32 product_count = 9;
+    repeated DiscountCategoryDto children = 10; // Recursive children
+}