code: public static RedmineManager createUnauthenticated(String uri,
                                                  HttpClient httpClient) {
          return createWithUserAuth(uri, null, null, httpClient);
      }
docs: Creates a non-authenticating redmine manager.
  
  @param uri    redmine manager URI.
  @param httpClient you can provide your own pre-configured HttpClient if you want
  to control connection pooling, manage connections eviction, closing, etc.