Add support for stateless user authentication in SimpleJWT

[wmeints]

Most SimpleJWT classes are supported in the OpenAPI spec, but the stateless user auth was missing. I've added it in this PR.
The stateless user auth is described here: https://django-rest-framework-simplejwt.readthedocs.io/en/latest/stateless_user_authentication.html

[tfranzel]

Hi, thx for the PR @wmeints . I would like to see a unit test for this. Ideally a short one without a full separate reference yaml.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.58%. Comparing base (b1a34b0) to head (b228b38).

❗ Current head b228b38 differs from pull request most recent head 84d86bd. Consider uploading reports for the commit 84d86bd to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1221   +/-   ##
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  Coverage   98.58%   98.58%           
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  Files          74       74           
  Lines        8886     8888    +2     
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+ Hits         8760     8762    +2     
  Misses        126      126           

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