/// <summary>
        /// Gets the ID of the rich menu linked to a user.
        /// </summary>
        /// <param name="userId">User ID. Found in the source object of webhook event objects. Do not use the LINE ID used in LINE.</param>
        /// <returns></returns>
        public async Task <string> GetRichMenuIDOfUserAsync(string userId)
        {
            //GET
            RichMenuResponseModel responseModel = new RichMenuResponseModel();
            string para      = $"/{userId}/richMenu";
            string apiResult = null;

            apiResult = await Utility.DoLineHttpGetAsync(MessagingApiUrl.UserSettingUrl, para, accessToken);

            responseModel = JsonConvert.DeserializeObject <RichMenuResponseModel>(apiResult);

            return(responseModel.richMenuId);
        }
        /// <summary>
        /// Gets a rich menu via a rich menu ID.
        /// </summary>
        /// <param name="richMenuId">ID of a rich menu</param>
        /// <returns></returns>
        public async Task <RichMenuResponseModel> GetRichMenuAsync(string richMenuId)
        {
            //GET
            RichMenuResponseModel responseModel = new RichMenuResponseModel();
            string para      = $"/{richMenuId}";
            string apiResult = null;

            apiResult = await Utility.DoLineHttpGetAsync(MessagingApiUrl.RichMenuUrl, para, accessToken);

            responseModel = JsonConvert.DeserializeObject <RichMenuResponseModel>(apiResult);

            return(responseModel);
        }
        /// <summary>
        /// Gets the ID of the default rich menu set with the Messaging API.
        /// </summary>
        /// <returns></returns>
        public async Task <RichMenuResponseModel> GetDefaultRichMenuIDAsync()
        {
            //GET
            RichMenuResponseModel responseModel = new RichMenuResponseModel();
            string para      = $"/all/richmenu";
            string apiResult = null;

            apiResult = await Utility.DoLineHttpGetAsync(MessagingApiUrl.UserSettingUrl, para, accessToken);

            responseModel = JsonConvert.DeserializeObject <RichMenuResponseModel>(apiResult);

            return(responseModel);
        }
        /// <summary>
        /// Creates a rich menu.
        /// </summary>
        /// <param name="richMenuModel">RichMenuModel</param>
        /// <returns></returns>
        public async Task <RichMenuResponseModel> CreateRichMenuAsync(RichMenuModel richMenuModel)
        {
            //POST
            RichMenuResponseModel responseModel = new RichMenuResponseModel();
            string apiResult  = null;
            string jsonString = JsonConvert.SerializeObject(richMenuModel);

            apiResult = await Utility.DoLineHttpPostAsync(MessagingApiUrl.RichMenuUrl, jsonString, accessToken);

            responseModel = JsonConvert.DeserializeObject <RichMenuResponseModel>(apiResult);

            return(responseModel);
        }