// 06. Export Sold Products
        public static string GetSoldProducts(ProductShopContext context)
        {
            var soldProducts = context.Users
                 .Where(u => u.ProductsSold.Any(ps => ps.Buyer != null))
                 .Select(u => new
                 {
                     firstName = u.FirstName,
                     lastName = u.LastName,
                     soldProducts = u.ProductsSold
                     .Where(ps => ps.Buyer != null)
                     .Select(ps => new
                     {
                         name = ps.Name,
                         price = ps.Price,
                         buyerFirstName = ps.Buyer.FirstName,
                         buyerLastName = ps.Buyer.LastName

                     })
                 })

                 .OrderBy(u => u.lastName)
                 .ThenBy(u => u.firstName)
                 .ToList();

            var jsonSoldProducts = JsonConvert.SerializeObject(soldProducts, Formatting.Indented);
            return jsonSoldProducts;
        }

        // 07. Export Categories By Products Count
        public static string GetCategoriesByProductsCount(ProductShopContext context)
        {
            var categoriesByProductsCount = context.Categories
                .Select(x => new
                {
                    category = x.Name,
                    productsCount = x.CategoryProducts.Count(),
                    averagePrice = $@"{x.CategoryProducts
                    .Sum(p => p.Product.Price) / x.CategoryProducts.Count():F2}",
                   totalRevenue = $"{x.CategoryProducts.Sum(p => p.Product.Price):F2}"
                })
                .OrderByDescending(x => x.productsCount)
                .ToList();

                var jsonCategoriesByProductsCount = JsonConvert.SerializeObject(categoriesByProductsCount, Formatting.Indented);
            return jsonCategoriesByProductsCount;
        }