public static string GetBooksByAuthor(BookShopContext context, string input)
        {
            StringBuilder sb = new StringBuilder();

            var booksAndAuthors = context
                .Books
                .Where(b => b.Author.LastName.ToLower()
                .StartsWith(input, StringComparison.OrdinalIgnoreCase))
                .OrderBy(b => b.BookId)
                .Select(b => new
                {
                    b.Title,
                    Author = $"{b.Author.FirstName} {b.Author.LastName}"
                })
                .ToList();

            foreach (var b in booksAndAuthors)
            {
                sb.AppendLine($"{b.Title} {b.Author}");
            }

            return sb.ToString().TrimEnd();
        }