The "/unsubscribe" page:
Users visit this page to be delisted from email alerts.
If a valid subscriber code is supplied in the name= query parameter, then that subscriber is delisted.
Otherwise, If the users is logged in, then they are redirected to the /alerts page where they have an unsubscribe button.
Non-logged-in users with no name= query parameter are invited to enter an email address to which will be sent the unsubscribe link that contains the correct subscriber code.