Allow HyperlinkedRelatedField to be used with related urls

[housleyjk]

Fixes #521

Description of the Change

The details in #521 are not clear, but I ran into a very similar SkipField issue when trying to use HyperlinkedRelatedFields and the RelatedMixin. The HyperlinkedRelatedField generates the correct url for the related link (e.g. /authors/1/entries), but visiting the url gives a 500 error because of an unhandled SkipField exception. In other words, without these changes, it is possible to give a related link in the payload, but that link won't actually work.

Checklist

• PR only contains one change (considered splitting up PR)
• unit-test added (I couldn't get the unit tests to all work prior to making these changes, but I was able to trigger and fix this issue with the existing test_retrieve_related_many() test. So this code is covered by unit tests.)
• NO documentation changes necessary, bug fix
• changelog entry added to CHANGELOG.md
• author name in AUTHORS

[sliverc]

Thanks @housleyjk This looks like a very reasonable fix. Testing should be improved though - see inline comments above.

[sliverc]

Not so ideal to change from ResourceRelatedField to HyperlinkedRelatedField as now the one but not the other will be tested.

Hence I think it would be better to add a new HyperlinkedRelatedField. Maybe comments could be used?

[codecov]

Codecov Report

Merging #529 into master will increase coverage by 0.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #529      +/-   ##
==========================================
+ Coverage   94.31%   94.33%   +0.01%     
==========================================
  Files          60       60              
  Lines        3713     3725      +12     
==========================================
+ Hits         3502     3514      +12     
  Misses        211      211

Impacted Files	Coverage Δ
example/models.py	90.9% <ø> (ø)	⬆️
example/settings/test.py	100% <100%> (ø)	⬆️
rest_framework_json_api/views.py	94.29% <100%> (+0.07%)	⬆️
example/tests/test_views.py	100% <100%> (ø)	⬆️
example/serializers.py	100% <100%> (ø)	⬆️

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[housleyjk]

Ok, I've improved the testing for this feature as requested and done my best to verify that it is correct. I hope you will forgive me renaming comment_set -> comments. I thought it was more consistent with the related name entries already in use.

[sliverc]

Thanks a lot @housleyjk I totally agree renaming comments to comment_set is much cleaner.