Add validation to prevent updates with duplicate national codes

src/CMSMicroservice.Application/UserCQ/Commands/UpdateUser/UpdateUserCommandHandler.cs

@@ -13,7 +13,7 @@ public class UpdateUserCommandHandler : IRequestHandler<UpdateUserCommand, Unit>
     {
         var entity = await _context.Users
             .FirstOrDefaultAsync(x => x.Id == request.Id, cancellationToken) ?? throw new NotFoundException(nameof(User), request.Id);
-        if (entity.NationalCode == request.NationalCode)
+        if (!string.IsNullOrWhiteSpace(request.NationalCode) && entity.NationalCode == request.NationalCode)
         {
             throw new Exception("کد ملی تکراری است");
         }