public static IDictionary<string, object> WithHeader(this IDictionary<string, object> env, string key, string value)
        {
            var request = new OwinRequest(env);
            request.SetHeader(key, value);

            return request.Dictionary;
        }
        public static IDictionary<string, object> WithBody(this IDictionary<string, object> env, Stream stream)
        {
            var request = new OwinRequest(env);
            request.Body = stream;
            request.SetHeader("Content-Length", stream.Length.ToString());

            return request.Dictionary;
        }