/// <summary>
        /// Adds middleware for using HSTS, which adds the Strict-Transport-Security header.
        /// </summary>
        /// <param name="app">The <see cref="IApplicationBuilder"/> instance this method extends.</param>
        public static IApplicationBuilder UseHsts(this IApplicationBuilder app)
        {
            HstsOptions options = new HstsOptions();

            return(app.UseMiddleware <HstsMiddleware>(options));
        }