code: public static String generateRegId(final String domainCreationDate, final String reverseDomainName,
              final String suffix) {
          if (StringUtils.isBlank(domainCreationDate)) {
              throw new SwidException("domainCreationDate isn't defined");
          }
          if (StringUtils.isBlank(reverseDomainName)) {
              throw new SwidException("reverseDomainName isn't defined");
          }
  
          StringBuilder res = new StringBuilder()
                  .append("regid")
                  .append(DELIMITER)
                  .append(domainCreationDate)
                  .append(DELIMITER)
                  .append(reverseDomainName);
          if (StringUtils.isNotBlank(suffix)) {
              res.append(",").append(suffix);
          }
  
          return res.toString();
      }
docs: Generate RegId with additional suffix.
  
  @param domainCreationDate
  the date at which the entity creating the regid first owned the domain that is also used in the regid
  in year-month format; e.g. 2010-04
  @param reverseDomainName
  the domain of the entity, in reverse order; e.g. com.labs64
  @param suffix
  additional sub-entities that are added as a suffix to the RegId
  @return generated RegId