public async Task <Product> AddProductAsync(Product product)
        {
            var result = await _context.AddAsync(product);

            if (await SaveAsync() > 0)
            {
                return(result.Entity);
            }
            return(null);
        }
        public async Task <PaymentPlan> AddPaymentPlanAsync(PaymentPlan paymentPlan)
        {
            var result = await _context.AddAsync(paymentPlan);

            if (await SaveAsync() > 0)
            {
                return(result.Entity);
            }
            return(null);
        }
        public async Task <Brand> AddBrandAsync(Brand brand)
        {
            var result = await _context.AddAsync(brand);

            if (await SaveAsync() > 0)
            {
                return(result.Entity);
            }
            return(null);
        }
        public async Task <Category> AddCategoryAsync(Category category)
        {
            var result = await _context.AddAsync(category);

            if (await SaveAsync() > 0)
            {
                return(result.Entity);
            }
            return(null);
        }