Add ToonDescription attributes for enhanced metadata support

Introduced Toon serialization/description attributes to CustomerDto, GenericAttribute, and OrderNote classes. Added table mapping and foreign key metadata, as well as necessary using statements, to improve serialization, documentation, and tooling capabilities.

Mango.Nop.Core/Dtos/CustomerDto.cs

@@ -1,8 +1,13 @@
-using Nop.Core.Domain.Common;
+using AyCode.Core.Serializers.Toons;
+using Nop.Core.Domain.Catalog;
+using Nop.Core.Domain.Common;
 using Nop.Core.Domain.Customers;
 
 namespace Mango.Nop.Core.Dtos;
 
+[LinqToDB.Mapping.Table(Name = nameof(Customer))]
+[System.ComponentModel.DataAnnotations.Schema.Table(nameof(Customer))]
+[ToonDescription($"Data transfer object for {nameof(Customer)}", TypeRelation = ToonTypeRelation.DtoOf, RelatedTypes = [typeof(Customer)])]
 public class CustomerDto : ModelDtoBase<Customer>, ISoftDeletedEntity
 {
     public string Username { get; set; }

Mango.Nop.Core/NopDependencies/Catalogs/GenericAttribute.cs

@@ -1,4 +1,6 @@
-namespace Nop.Core.Domain.Common;
+using AyCode.Core.Serializers.Toons;
+
+namespace Nop.Core.Domain.Common;
 
 /// <summary>
 /// Represents a generic attribute
@@ -8,6 +10,8 @@ public partial class GenericAttribute : BaseEntity
     /// <summary>
     /// Gets or sets the entity identifier
     /// </summary>
+    ///
+    [ToonDescription(Constraints = "polymorphic-fk(KeyGroup)")]
     public int EntityId { get; set; }
 
     /// <summary>

Mango.Nop.Core/NopDependencies/Catalogs/OrderNote.cs

@@ -1,4 +1,6 @@
-namespace Nop.Core.Domain.Orders;
+using AyCode.Core.Serializers.Toons;
+
+namespace Nop.Core.Domain.Orders;
 
 /// <summary>
 /// Represents an order note
@@ -8,6 +10,7 @@ public partial class OrderNote : BaseEntity
     /// <summary>
     /// Gets or sets the order identifier
     /// </summary>
+    [ToonDescription($"Foreign key to parent {nameof(Order)}", ForeignKey = nameof(Order))]
     public int OrderId { get; set; }
 
     /// <summary>