public async Task InsertProduct(AddProductDTO productDTO)
        {
            var product = new Product
            {
                Id          = productDTO.ProductId,
                Name        = productDTO.Name,
                ProductType = (ProductType)Enum.Parse(typeof(ProductType), productDTO.ProductType, true),
                Price       = productDTO.Price
            };

            this.dbContext.Products.Add(product);
            await dbContext.SaveChangesAsync();
        }
        public async Task InsertCustomer(AddCustomerDTO addCustomerDTO)
        {
            var customer = new Customer
            {
                Id        = addCustomerDTO.Id,
                Username  = addCustomerDTO.Username,
                Password  = addCustomerDTO.Password,
                Email     = addCustomerDTO.Email,
                FirstName = addCustomerDTO.FirstName,
                LastName  = addCustomerDTO.LastName
            };

            this.dbContext.Customers.Add(customer);
            await dbContext.SaveChangesAsync();
        }