public async Task <TResponse> Post <TRequest, TResponse>(string url, TRequest request)
where TRequest : Request where TResponse : Response
{
const string jsonMediaType = "application/json";
var data = new StringContent(_jsonParser.ToJson(request), Encoding.UTF8, jsonMediaType);
var response = await _client.PostAsync(url, data);
var contents = await response.Content.ReadAsStringAsync();
return(_jsonParser.FromJson <TResponse>(contents));
}