code: private static String decodeFormFields(final String content, final Charset charset) {
          if (content == null) {
              return null;
          }
  
          return urlDecode(content, (charset != null) ? charset : Charsets.UTF_8, true);
      }
docs: Decode/unescape www-url-form-encoded content.
  
  @param content
  the content to decode, will decode '+' as space
  @param charset
  the charset to use
  @return encoded string