public Dictionary<string, object> RenewAccessToken(string refreshToken)
{
RestRequest request = new RestRequest("_oauth2/token", Method.POST);
request.AddParameter("client_id", ClientId);
request.AddParameter("client_secret", ClientSecret);
request.AddParameter("refresh_token", RefreshToken);
request.AddParameter("grant_type", "refresh_token");
Response response = Execute(request);
Dictionary<string, object> responseDictionary = response.Deserialize<Dictionary<string, object>>();
AccessToken = (string)responseDictionary["access_token"];
RefreshToken = (string)responseDictionary["refresh_token"];
return responseDictionary;
}