Support for Cabotage deployments

[JacobCoffee]

Initial support for migrating from Heroku (paid) to Cabotage (free)

Needs these set it cabo ui

• GH_SECRET
• GH_APP_ID
• GH_PRIVATE_KEY
• SENTRY_DSN
• REDIS_URL (new, replacing the Heroku-specific one)
• GH_AUTH

Will require disabling Heroku deploy -> enabling cabotage
it is ready @ https://cabotage.us-east-2.psfhosted.computer/projects/python/miss-islington/applications/miss-islington

Will also require Redis setup in k8s

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (8a66b2f) to head (47e850f).
⚠️ Report is 12 commits behind head on main.

@@            Coverage Diff            @@
##              main      #729   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            6         6           
  Lines          337       337           
  Branches        12        12           
=========================================
  Hits           337       337           

Flag	Coverage Δ
Python_3.11	100.00% <100.00%> (ø)
Python_3.12	100.00% <100.00%> (ø)
Python_3.13	100.00% <100.00%> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
tests/test_backport_pr.py	100.00% <100.00%> (ø)
tests/test_delete_branch.py	100.00% <100.00%> (ø)

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[JacobCoffee]

• added vars

- generated Redis instance - applied k8s config.

i think all that's left/needed is to deploy cabo app, flip gh app webhook url:
(inmiss-islington GitHub App settings, change the webhook URL to:)

https://python-miss-islington-miss-islington-web.ingress.us-east-2.psfhosted.computer

and then we can easily flip back if something is wrong

basically:

1. Deploy to cabotage, let it run idle
2. Flip the webhook URL in the GitHub App settings to cabo
3. Watch for a bit
4. If something breaks, flip the URL back to Heroku
5. kill heroku when success

[webknjaz]

It'd be a good idea to retrieve the short-lived tokens via the GH App.. Here's what I have in Patchback: https://github.com/sanitizers/patchback-github-app/blob/5bd473a3e3593039610c8be502c011fbe0e21306/patchback/event_handlers.py#L129C35-L129C60. Of course, this is out of scope right now, something to think about in the future.

[StanFromIreland]

Does this need anything else before we can test it? (Although I'd suggest we do so in a week or two, after 3.15 is released.)