Perform additional setup after user have been logged in.

def account_setup(remote, token, resp):
    """Perform additional setup after user have been logged in."""
    resource = get_resource(remote)

    with db.session.begin_nested():
        person_id = resource.get('PersonID', [None])
        external_id = resource.get('uidNumber', person_id)[0]

        # Set CERN person ID in extra_data.
        token.remote_account.extra_data = {
            'external_id': external_id,
        }
        groups = account_groups_and_extra_data(token.remote_account, resource)
        assert not isinstance(g.identity, AnonymousIdentity)
        extend_identity(g.identity, groups)

        user = token.remote_account.user

        # Create user <-> external id link.
        oauth_link_external_id(user, dict(id=external_id, method='cern'))