docs: public static StringBuilder makePage(final String htmlheader,
                                         final String title,
                                         final String subtitle,
                                         final String body) {
      final StringBuilder buf = new StringBuilder(
        BOILERPLATE_LENGTH + (htmlheader == null ? 0 : htmlheader.length())
        + title.length() + subtitle.length() + body.length());
      buf.append(PAGE_HEADER_START)
        .append(title)
        .append(PAGE_HEADER_MID);
      if (htmlheader != null) {
        buf.append(htmlheader);
      }
      buf.append(PAGE_HEADER_END_BODY_START)
        .append(subtitle)
        .append(PAGE_BODY_MID)
        .append(body)
        .append(PAGE_FOOTER);
      return buf;
    }