Subscription confirmation

[rossjrw]

A user should receive a subscription confirmation on the next hourly channel after their initial sign up.

Documentation on the site should lead the user to expect to receive this confirmation that their subscription is set up correctly.

I'll need to research how best to implement this, as it's crucial I only ever send each user one confirmation, no matter what. This is absolutely a solved problem. That being said, instinct tells me I should track a positive value when I add a new user and then remove it when that user is confirmed. This makes the 'default case' a user who is already confirmed, so should hopefully prevent me from ever accidentally sending a confirmation - because to send one, I need to explicitly opt in.

[rossjrw]

Also, could be good to do something similar for when a user changes their delivery method, to confirm the new one is valid