The usual stuff! Installed the new gem and its new deps, ran
`bin/rails app:update` and did my best to manually merge the dev/prod
config files with the new canonical defaults, deleted some migrations I
don't think are relevant to us, and yeah!
Also, Rails 7.1 seems to need `libyaml-dev` installed, so I added that
to the `deploy/setup.yml` playbook!
One thing to note is that, while I was here, I turned on some settings
relating to our use of SSL that technically weren't on before. This
should be fine and helpful? But if stuff breaks, well, check those!
This one was pretty straightforward yaay! Main thing was the change from `render file` to `render template` in a couple places, oh and a thing with complex `order()` clauses.
