chore: Add async linting

[suejung-sentry]

The Django postgres ORM is synchronous but the GraphQL resolvers are asynchronous. When any ORM commands are attempted to run directly within a resolver, this causes a runtime error You cannot call this from an async context - use a thread or sync_to_async.

I investigated different ways we could potentially use lint or type-check tools or even just a unit test that could catch these errors before they hit prod. Unfortunately I had trouble getting anything that could work reliably, and plug in with our existing tools (ruff, mypy, pytest). I explored the below:

• mypy django-stubs plugin, with enable-async-orm-checks = True - https://github.com/typeddjango/django-stubs - running this plugin pointed at our configurations could not resolve our django settings
• pylint custom plugin (ruff doesn't allow custom plugin) - this required adding support for pylint on top of ruff to get custom plugin functionality - but even trying one out I couldn't get a simple test case to work for our needs
• unit test that traverses resolver functions - this resulted in too many false positives

So in the end I just added in the off-the-shelf async linter offered by flake8 that can catch common errors with async. Unfortunately it doesn't solve the original reason for this investigation re: Django ORM, but can at least be a backstop for other async related pitfalls.

I've also added this "runbook" for on-call or debugging response related to graphQL/async in api

Closes codecov/engineering-team#2473

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Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.03%. Comparing base (70b4692) to head (b8d4986).
Report is 1 commits behind head on main.

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  Coverage   96.03%   96.03%           
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  Files         827      827           
  Lines       19071    19071           
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  Hits        18315    18315           
  Misses        756      756           

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[ajay-sentry]

nit: maybe this should be "performance anti-pattern rules" and the rules link should be above

[suejung-sentry]

oh woops, I misread what the original comment was trying to convey haha. Fixed!

[ajay-sentry]

haha no worries

[ajay-sentry]

lgtm! Happy to see we didn't have any errors for this guy either 😅