docs: protected void addUserAgentRequestHeader(HttpState state,
                                               HttpConnection conn)
      throws IOException, HttpException {
          LOG.trace("enter HttpMethodBase.addUserAgentRequestHeaders(HttpState, "
              + "HttpConnection)");
  
          if (getRequestHeader("User-Agent") == null) {
              String agent = (String)getParams().getParameter(HttpMethodParams.USER_AGENT);
              if (agent == null) {
                  agent = "Jakarta Commons-HttpClient";
              }
              setRequestHeader("User-Agent", agent);
          }
      }