code: public @Nonnull StaticMessageSource addMessage(@Nonnull String code, @Nonnull String message) {
          if (StringUtils.isNotEmpty(code) && StringUtils.isNotEmpty(message)) {
              messageMap.put(new MessageKey(Locale.getDefault(), code), message);
          }
          return this;
      }
docs: Adds a message to the default locale.
  @param code The code
  @param message The the message
  @return This message source