As the comment in `deploy.yml` explains, this was a multi-step process,
but it went very smoothly as planned, hooray!!
I noticed again while making this change that Bundler doesn't seem to
be availing itself of the checked-in dependencies in `vendor/cache`. I
think I know the fix for this, I'll toss it into an upcoming change and
see if it works!
Hey nice! We have to add webrick now because it's not included in Ruby 3, but hey just drop it right back in.
Idk how to choose between this or puma or whatever, but in the absence of a specific reason let's just pick the one whose name I know best.
Some tricks required here to get the dependencies to work out, but we got it!!
Oh also, we move away from the rbenv in Ubuntu's package manager, because it doesn't support more recent Rubies like 2.4.10.
NOTE: This doesn't boot yet! There's something changed in the `devise` API that we'll need to fix!
```
/vagrant/config/initializers/devise.rb:46:in `block in <top (required)>': undefined method `encryptor=' for Devise:Module (NoMethodError)
```
But yeah, we navigated the gem upgrades, and also I ran `rake rails:update` and hand-processed the suggestions it had for our config files.
