ci: add 3.12 and caching pip dependencies

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (d97b79b) 100.00% compared to head (217bbe4) 100.00%. Report is 6 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #20 +/- ## ========================================= Coverage 100.00% 100.00% ========================================= Files 2 2 Lines 154 154 ========================================= Hits 154 154 ``` | [Flag](https://app.codecov.io/gh/k4black/fastapi-jwt/pull/20/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Konstantin+Chernyshev) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/k4black/fastapi-jwt/pull/20/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Konstantin+Chernyshev) | `?` | | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Konstantin+Chernyshev#carryforward-flags-in-the-pull-request-comment) to find out more.

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