Handle http method names passed for views in DRF for correct schema generation

[jekel]

DRF does not handle 'http_method_names' argument for as_view() constructor when returning allowed method names for a view/endpoint, so if you pass explicitly any, schema will be generated by all existing, not only allowed.
These changes below correctly handle this issue.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (f31238e) 98.62% compared to head (df5a4fc) 98.58%.

❗ Current head df5a4fc differs from pull request most recent head 38507c6. Consider uploading reports for the commit 38507c6 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1075      +/-   ##
==========================================
- Coverage   98.62%   98.58%   -0.05%     
==========================================
  Files          71       68       -3     
  Lines        8609     8483     -126     
==========================================
- Hits         8491     8363     -128     
- Misses        118      120       +2     

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[jekel]

@tfranzel are there any chances that pull request will be accepted?

[tfranzel]

@jekel yeah sorry, didn't have much time recently and this is a non-trivial change. I will thoroughly look at it asap.

[tfranzel]

sry this took so long to get merged.

I slightly changed theif because the initkwarg should be used if present, not just when truthy.
Otherwise excellent PR! 🚀 Thanks @jekel for the effort and the patience.