code: public static void setSlugHeader(HttpHeaders headers, String value) {
      if (value == null) {
        headers.remove("Slug");
      } else {
        headers.set("Slug", Lists.newArrayList(Arrays.asList(SLUG_ESCAPER.escape(value))));
      }
    }
docs: Sets the {@code "Slug"} header, properly escaping the header value. See <a
  href="http://tools.ietf.org/html/rfc5023#section-9.7">The Slug Header</a>.
  
  @since 1.14