Set up rotation for encrypted API tokens

[connorshea]

In Rails 7, the the default digest class for the key generator changed from SHA1 to SHA256, but we're still on SHA1.

In order to finish the Rails 7 upgrade tasks (even though we're on 7.1 right now), we have to register a rotator for the encrypted messages we store, and then rotate them.

Need to test this heavily to ensure it actually works before shipping it, then we can bump the load_defaults from 6.1 to 7.0, and then move forward to Rails 7.2 in the future.

https://guides.rubyonrails.org/v7.0/upgrading_ruby_on_rails.html#key-generator-digest-class-changing-to-use-sha256