docs: public FormDataParser createParser(final HttpServerExchange exchange) {
          FormDataParser existing = exchange.getAttachment(ATTACHMENT_KEY);
          if(existing != null) {
              return existing;
          }
          for (int i = 0; i < parserDefinitions.length; ++i) {
              FormDataParser parser = parserDefinitions[i].create(exchange);
              if (parser != null) {
                  exchange.putAttachment(ATTACHMENT_KEY, parser);
                  return parser;
              }
          }
          return null;
      }