fix: let use a default value for foreignkey model field

[freddez]

If there is a default value in a model foreign key ('0' im my case), the actual code calls field.to_representation(field.default) and tries to interpret field.default.pk and raises an error. This fix let use raw default value.

See Django documentation : https://docs.djangoproject.com/en/4.1/ref/models/fields/#default

For fields like ForeignKey that map to model instances, defaults should be the value of the field they reference (pk unless to_field is set) instead of model instances.

[tfranzel]

Tox is broken since yesterdays release. Upstream issue is already raised. I will review this in the next couple of days.

[codecov]

Codecov Report

Base: 98.70% // Head: 98.70% // No change to project coverage 👍

Coverage data is based on head (f6929d0) compared to base (7bfcfb1).
Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #901   +/-   ##
=======================================
  Coverage   98.70%   98.70%           
=======================================
  Files          68       68           
  Lines        7936     7936           
=======================================
  Hits         7833     7833           
  Misses        103      103           

Impacted Files	Coverage Δ
drf_spectacular/openapi.py	97.68% <100.00%> (ø)

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[freddez]

Hello,
could you integrate or reject this pull request ?

[tfranzel]

sry @freddez this took a while for me to get around to. thank you for the PR

Actually this got drive-by fixed in #936, due to a "bug" in DRF. However, I think it makes sense to include and also add SlugRelatedField for consistency and clarity even though the outcome would be the same.