Implement TLS ASGI extension

[mdgilene]

Checklist

• There are no similar issues or pull requests for this yet.
• I discussed this idea on the community chat and feedback is positive.

Is your feature related to a problem? Please describe.

No

Describe the solution you would like.

Implementation of the TLS ASGI extension. Recently this extension has been formalized via django/asgiref#192. It would be nice to get this implemented in Uvicorn so that applications can start using this info.

Describe alternatives you considered

N/A

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[Kludex]

PR is welcome. We are blocked until next asgiref release.

[brussee]

@Kludex wrote:

PR is welcome. We are blocked until next asgiref release.

I noticed the ASGI TLS Extension version 0.2 (2020-10-02) was merged on 2021-07-10 and subsequently a new asgiref version 3.5.0 was recently released on 2022-01-22. Does this mean we are no longer blocked and this PR of @mdgilene can be polished and merged? :-)