Chore: Update app to Rails 7

[ChargrilledChook]

Given we're now teaching Rails 7 it would be good to have parity with the app too.

Official upgrade guide

Todo

• Chore: Update config files for Rails 7 -> Chore: Begin Rails 7 upgrade #3608
• Chore: Set app defaults to Rails 7 #3797
• Chore: Prepare app for Devise / Turbo incompatibility issues - reference for one solution to compatibility issues
• Chore: Prepare app for switch to Hotwire
• Fix: Any new deprecations caused by Rails 7 update
• Chore: Remove UJS / old JS dependencies
• Chore: Update Oauth2 #3057
• Chore: Upgrade to Webpacker 6 #3017
• Chore: Remove temporary gems from Gemfile #2884 -> Chore: Begin Rails 7 upgrade #3608

Notes

• Now Chore: Begin Rails 7 upgrade #3608 is merged the app is running on Rails 7, but there is still some follow up work to do.
• Devise incompatibility may no longer be an issue

[ChargrilledChook]

There's a somewhat vague instruction in the upgrade guide

"Change the versions for Rails JavaScript packages in package.json and run yarn install, if running on Webpacker."

But no obvious info on where to find relevant versions. It is probably worth removing UJS, though

[KevinMulhern]

Thanks for getting this started @ChargrilledChook 💪

Should we break some chores out of this?

• Chore for fixing the oauth2 depreciation
• Maybe another for getting Hotwire in the app with turbo turned off.
• Another for replacing any Rails ujs behaviour we use.
  etc

[ChargrilledChook]

Thanks for getting this started @ChargrilledChook muscle

My pleasure 🔧

Should we break some chores out of this?

Great idea, I'll spin up a few issues out of this and keep track of them in this one

[ChargrilledChook]

Updated OP now #3608 is merged with some follow up work to do

[ChargrilledChook]

Outside of enabling Turbo, the app is now completely on Rails 7. I've opened a new story for the Turbo changes #3806