code: public boolean isDefaultGroup(String groupName) {
  
          if (CmsStringUtil.isEmptyOrWhitespaceOnly(groupName)) {
              return false;
          }
  
          // first check without ou prefix, to stay backwards compatible
          boolean isDefault = m_groupAdministrators.equals(groupName);
          isDefault = isDefault || m_groupGuests.equals(groupName);
          isDefault = isDefault || m_groupUsers.equals(groupName);
  
          // now check with ou prefix
          isDefault = isDefault || groupName.endsWith(CmsOrganizationalUnit.SEPARATOR + m_groupAdministrators);
          isDefault = isDefault || groupName.endsWith(CmsOrganizationalUnit.SEPARATOR + m_groupGuests);
          isDefault = isDefault || groupName.endsWith(CmsOrganizationalUnit.SEPARATOR + m_groupUsers);
  
          return isDefault;
      }
docs: Checks if a given group name is the name of one of the OpenCms default groups.<p>
  
  @param groupName the group name to check
  @return <code>true</code> if group name is one of OpenCms default groups, <code>false</code> if it is not
  or if <code>groupName</code> is <code>null</code> or an empty string (no trim)
  
  @see #getGroupAdministrators()
  @see #getGroupUsers()
  @see #getGroupGuests()