code: private static String encodeFormFields (final String content, final String charset) {
          if (content == null) {
              return null;
          }
          return urlencode(content, charset != null ? Charset.forName(charset) :
              Consts.UTF_8, URLENCODER, true);
      }
docs: Encode/escape www-url-form-encoded content.
  <p>
  Uses the {@link #URLENCODER} set of characters, rather than
  the {@link #UNRSERVED} set; this is for compatibilty with previous
  releases, URLEncoder.encode() and most browsers.
  
  @param content the content to encode, will convert space to '+'
  @param charset the charset to use
  @return