⬆ Add support for Python 3.9

[Kludex]

Pydantic added support to Python 3.9 last week on this PR.

TODO:

• Add tests with the new typing feature i.e. dict[int]

Notes:

• I haven't talked to @tiangolo about this PR and I don't know his wishes towards this support. Please, do not assume this will be merged.
• Parametrize was not possible in the tests due to incompatibility of notation on Python versions and the fact that Pytest gets to discover the code even if the skipif mark is used.

[codecov]

Codecov Report

Merging #2298 (e37ad3d) into master (e9ba01d) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master     #2298   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files          408       409    +1     
  Lines        10229     10244   +15     
=========================================
+ Hits         10229     10244   +15     

Impacted Files	Coverage Δ
..._sql_databases_peewee/test_sql_databases_peewee.py	100.00% <100.00%> (ø)
tests/test_typing_python39.py	100.00% <100.00%> (ø)
tests/test_union_inherited_body.py	100.00% <100.00%> (ø)
fastapi/utils.py	100.00% <0.00%> (ø)

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[github-actions]

📝 Docs preview for commit 5669a2b at: https://5fa32e2b16c730102e69945a--fastapi.netlify.app

[github-actions]

📝 Docs preview for commit 7f329e2 at: https://5fa33361d0bdc30c81f6f47d--fastapi.netlify.app

[github-actions]

📝 Docs preview for commit cbdd4b9 at: https://5fa34c5e0b2657362e5b83f1--fastapi.netlify.app

[tiangolo]

This is awesome! 🚀 I'm gonna check it in detail thoroughly later, I was actually expecting a lot of internal changes to support it 😅

[tiangolo]

Great, thanks @Kludex! 🚀