Upgrading from 2.2.x - tank_auth

Hi all,

I've recently resurrected an old side project due to covid boredom. I made significant progress on it years ago and then forgot about it for a while. At the time it was on CI 1.7.2.

Over the last couple of weeks, I've successfully upgraded it to CI 2.1.4 (three rounds of lib upgrades so far), and with the move to a new server that has php-mcrypt, I'll be able to upgrade it to CI 2.2.x in the next couple of days.

After that I'm a bit at a loss because I've been using tank_auth for users, and it doesn't look like that is compatible with CI 3.x. 

Does anyone have any advice on what I should do next, particularly regarding authentication? I'm not sure of the effects of upgrading to either CI 3.x or 4.x, but I'd hate to make my users have to all generate new passwords. Does anyone have experience moving from tank_auth to something else?

Thanks!