def remember(environ, identity):
    """ On egress (no challenge required):

        args -> [ (header-name, header-value), ...] | None

        Return a list of headers suitable for allowing the requesting
        system to remember the identification information (e.g. a
        Set-Cookie header).  Return None if no headers need to be set.
        These headers will be appended to any headers returned by the
        downstream application.
        """
