'Return the identifier used with tags to link this user.'

@property
def tag_value(self):

    if self.ident:
        return u'id:{}'.format(self.ident)
    if self.email:
        return u'email:{}'.format(self.email)
    if self.username:
        return u'username:{}'.format(self.username)
    if self.ip_address:
        return u'ip:{}'.format(self.ip_address)
