docs: protected RelationKey parseRelationKey(String id) {
  
          Matcher matcher = RELATION_PATTERN.matcher(id);
          matcher.find();
          CmsUUID src = new CmsUUID(matcher.group(1));
          CmsUUID tgt = new CmsUUID(matcher.group(2));
          String tp = matcher.group(3);
          return new RelationKey(src, tgt, tp);
      }