code: func (s *IdentityService) DeleteUser(user string) error {
  	_, err := s.GetUser(user)
  	if err != nil {
  		return trace.Wrap(err)
  	}
  	startKey := backend.Key(webPrefix, usersPrefix, user)
  	err = s.DeleteRange(context.TODO(), startKey, backend.RangeEnd(startKey))
  	return trace.Wrap(err)
  }
docs: // DeleteUser deletes a user with all the keys from the backend