docs: @Override
      public <T> T putAttachment(final AttachmentKey<T> key, final T value) {
          if (key == null) {
              throw UndertowMessages.MESSAGES.argumentCannotBeNull("key");
          }
          if(attachments == null) {
              attachments = createAttachmentMap();
          }
          return (T) attachments.put(key, value);
      }