code: static protected String encodeHeaderValue(String userMetaValue) {
          try {
              String encodedValue = HEADER_VALUE_PREFIX + URLEncoder.encode(userMetaValue, UTF_8);
              return encodedValue;
          } catch (UnsupportedEncodingException e) {
              //this should never happen
              throw new RuntimeException(e);
          }
      }
docs: Ensures compliance with  https://tools.ietf.org/html/rfc5987#section-3.2.2
  
  @param userMetaValue
  @return