postMessage method
Sends an HTTP POST request at the given path with the given message as request body.
The given path will be concatenated with the _baseUrl.
Implementation
Future<http.Response> postMessage(UrlPath path, GeneratedMessage message) {
var uri = _toAbsoluteUri(path);
String preparedBody = _translator.body(uri, message);
var preparedHeaders = _translator.headers(uri);
var response = http.post(uri, body: preparedBody, headers: preparedHeaders);
return response;
}