docs: def by_mail(self, mail, archived=False, limit=None, page=None):
          """ lookup users by mail address.
          you may do in two ways:
              - specify one address: foo@bar.com
              - specify a domain   : @bar.com
          both will return a list.
  
          the role 'Zeiterfasser' may not lookup users.
          """
          path = partial(_path, self.adapter)
          if not archived:
              path = _path(self.adapter)
          else:
              path = _path(self.adapter, 'archived')
          return self._get(path, email=mail, limit=limit, page=page)