code: @Override
      public Set<String> getPossibleUserAttributeNames() {
          final Set<String> names = new HashSet<String>();
          names.addAll(this.possibleUserAttributes);
          names.addAll(localAccountDao.getCurrentAttributeNames());
          names.add(displayNameAttribute);
          return names;
      }
docs: Return the list of all possible attribute names. This implementation queries the database to
  provide a list of all mapped attribute names, plus all attribute keys currently in-use in the
  database.
  
  @return Set