Add Rails 8.1 style local CI via bin/ci

[larouxn]

Description

Proposing we add a bin/ci local CI tool, a new Rails feature as of Rails 8.1, for local sanity checks. For example, peeps can run bin/ci before pushing to check basic app setup, linting, security, and unit tests are all good prior to handing such off to hosted CI.

Notes

• I've have not enabled seed tests as they fail due to needing AWS credentials and I've not enabled system tests as they take a while and generally are a bit flaky even requiring retries in hosted CI to pass. This is meant as a quick local CI sanity check anyway.
• In an ideal world both the seed test and system tests would run well locally and this local CI would fully replicate hosted CI. At which point we could even replace the hosted (GitHub Actions) CI config "run" step with the bin/ci, ensuring that they're one and the same. And in that case we could even proceed with adding gh signoff and/or requiring bin/ci pass before push via a Git commit hook. Many possible enhancements. 🙂
• This along with Upgrade from Rails 8.0 to 8.1 defaults #6427 wrap up our Rails 8.1 upgrade i.e. bin/rails app:update is complete and we're fully up-to-date.

References

• https://guides.rubyonrails.org/8_1_release_notes.html#local-ci
• https://www.fastruby.io/blog/rails-8-1-local-ci.html
• https://derails.dev/blog/rails-local-ci/

Follow up to:

• Upgrade from Rails 8.0.5 to 8.1.3 #6335

Testing

Have tested using this locally quite a few times.

[larouxn]

This bin/herb comes from herb itself.

https://github.com/marcoroth/herb/blob/fac8b7b7e729be4b9a7213e602213242979ea794/bin/herb

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.51%. Comparing base (0107fd4) to head (b16e6bc).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6428      +/-   ##
==========================================
- Coverage   97.07%   94.51%   -2.56%     
==========================================
  Files         494      494              
  Lines       10514    10573      +59     
==========================================
- Hits        10206     9993     -213     
- Misses        308      580     +272     

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