docs: @Nullable
    public static String getHttpUserAgentStringFromRequest (@Nonnull final HttpServletRequest aHttpRequest)
    {
      // Use non-standard headers first
      String sUserAgent = aHttpRequest.getHeader (CHttpHeader.UA);
      if (sUserAgent == null)
      {
        sUserAgent = aHttpRequest.getHeader (CHttpHeader.X_DEVICE_USER_AGENT);
        if (sUserAgent == null)
          sUserAgent = aHttpRequest.getHeader (CHttpHeader.USER_AGENT);
      }
      return sUserAgent;
    }