public static void Set(this HttpContentHeaders headers, string name, string value)
        {
            if (headers == null)
            {
                throw new ArgumentNullException(nameof(headers));
            }

            headers.Set(name, new[] { value });
        }
        public static void Set(this HttpContentHeaders headers, string name, params string[] values)
        {
            if (headers == null)
            {
                throw new ArgumentNullException(nameof(headers));
            }

            headers.Set(name, (IEnumerable <string>)values);
        }