Upgrade to Rails 6.2

[nikolai-b]

Rails 7 is live so we want to move to the latest Rails 6 we can.

Declarative authorization which we use for our permissions is stuck on Rails 4. We are using a patched version that works with Rails 6.0 but not 6.1. To upgrade we should move our permissions model to pundit or CanCanCan.

This would mean migrating our authorization_rules and swapping all the permitted_to in our view code.