✨ Add support for lifespan async context managers (superseding startup and shutdown events)

[uSpike]

This adds support for the lifespan argument to the application and router, which was added in starlette.

I tidied up some of the event tests as well to promote reuse.

Fixes #2943

[github-actions]

📝 Docs preview for commit 8c33c94 at: https://604c4976cfdb60814a49803c--fastapi.netlify.app

[codecov]

Codecov Report

Patch coverage: 100.00% and no project coverage change

Comparison is base (cf73051) 100.00% compared to head (12e924d) 100.00%.

❗ Current head 12e924d differs from pull request most recent head 6adb554. Consider uploading reports for the commit 6adb554 to get more accurate results

Additional details and impacted files

@@             Coverage Diff             @@
##            master     #2944     +/-   ##
===========================================
  Coverage   100.00%   100.00%             
===========================================
  Files          540       243    -297     
  Lines        13969      7441   -6528     
===========================================
- Hits         13969      7441   -6528     

Impacted Files	Coverage Δ
fastapi/routing.py	100.00% <ø> (ø)
fastapi/applications.py	100.00% <100.00%> (ø)
tests/test_router_events.py	100.00% <100.00%> (ø)
fastapi/params.py	100.00% <0.00%> (ø)
fastapi/encoders.py	100.00% <0.00%> (ø)
tests/test_query.py	100.00% <0.00%> (ø)
fastapi/responses.py	100.00% <0.00%> (ø)
fastapi/exceptions.py	100.00% <0.00%> (ø)
fastapi/websockets.py	100.00% <0.00%> (ø)
... and 342 more

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[github-actions]

📝 Docs preview for commit 12e924d at: https://604c4d9c53c6988fd2efed45--fastapi.netlify.app

[nesb1]

Hi, we really need this fix, can i help with PR? There is a conflict @uSpike

[meshantz]

I rebased, dealt with the commit conflicts and updated a test in #4147

[Kludex]

@meshantz There's no need for that. If @uSpike is not able to rebase, @tiangolo will eventually see this PR and rebase himself. 😗

[meshantz]

One of the tests that was added was failing due to a starlette update. Saw that nothing had happened in the last 15 days, and was hoping to lend a hand.

I'd also like to see this get implemented, as it's much nicer than referencing the global app from inside of a startup or shutdown handler.

[uSpike]

Hi, sorry I've been out of the loop for a bit. I've rebased and cherry-picked @meshantz commit f5f1bfc into this PR.

[uSpike]

I've fixed typing, formatting, and updated the docs to communicate that lifespan should be an AsyncContextManager. Should be ready for review now.

[mortbauer]

@tiangolo this seems like a straight forward PR, please have a look if you can, would be great!!

[github-actions]

📝 Docs preview for commit 5ae6547 at: https://64062412c1f3f7106eff7bd8--fastapi.netlify.app

[github-actions]

📝 Docs preview for commit 8b6dd1a at: https://640626d9f5524310c7db8154--fastapi.netlify.app

[tiangolo]

Thank you @uSpike! 🙇 🍰

I updated the docs to include more info and make this the recommended way from now on.

I also took the updates in #5503, thanks @JonathanPlasse ! ☕

And I added tests for the new example in the docs.

This will be available in FastAPI 0.93.0, released in the next few hours. 🎉

Sorry for the long delay! 🙈 I wanted to personally address each issue/PR and they piled up through time, but now I'm checking each one in order.