Right, I had that idea while writing the comment, then forgot to actually do it lmao
This is important for session expiration: we don't want you to be able to hold onto an old cookie for an account that you should be locked out of. Updating the `createdAt` value requires a new signature, so the client can't forge when this token was created, so we can be confident in our ability to expire them.
Okay so one of the trickiest parts of login is done! 🤞 and now we need to make it actually show up in the UI. (and also pressure-test the security a bit, I've only really checked the happy path!)
