Notifications Email: Turn off without login

[FinnWoelm]

As a user, I want to be able to disable email notifications from within an email notification without having to log in. This feature will be beneficial to us as well because we will have more users opting-out and fewer users marking our emails as spam.

Ideally, the link should use a secure token and lapse after one week. If opted out, email the user that they were opted out of email notifications. This is to avoid the scenario where they forwarded the email to a friend and the friend opts them out even though they did not want to.