Respect serializer's id field.

[amw]

Description of the Change

Until now the renderer ignored id field provided by the serializer. This prevented API author from using separate values for internal database key (pk) and for user facing resource ID. One reason for using separate values like this is if the pk has to be small for use by foreign keys and external id can be longer, for example a human readable string.

Checklist

• PR only contains one change (considered splitting up PR)
• unit-test added
• documentation updated
• CHANGELOG.md updated (only for user relevant changes)
• author name in AUTHORS

[sliverc]

This PR seems to be related to issue #155

For complete support to overwrite primary key of a resource it also needs to be possible to reference such in relationships. How would you go about this with your approach?
Other question is also how the view would need to look like for custom primary key lookup?

[Datamance]

What is the recommended workaround for this, for the time being?

Glad this is being worked on!

[codecov]

Codecov Report

Merging #576 into master will decrease coverage by 0.47%.
The diff coverage is 95%.

@@            Coverage Diff             @@
##           master     #576      +/-   ##
==========================================
- Coverage   96.11%   95.64%   -0.48%     
==========================================
  Files          56       55       -1     
  Lines        2859     2870      +11     
==========================================
- Hits         2748     2745       -3     
- Misses        111      125      +14

Impacted Files	Coverage Δ
rest_framework_json_api/renderers.py	87.45% <100%> (+0.66%)	⬆️
example/tests/unit/test_renderer_class_methods.py	98.83% <94.11%> (-1.17%)	⬇️
rest_framework_json_api/metadata.py	25% <0%> (-23.34%)	⬇️
example/tests/test_filters.py	100% <0%> (ø)	⬆️
example/settings/dev.py	100% <0%> (ø)	⬆️
example/tests/integration/test_pagination.py	100% <0%> (ø)	⬆️
example/tests/integration/test_polymorphism.py	100% <0%> (ø)	⬆️
example/models.py	100% <0%> (ø)	⬆️
example/tests/test_serializers.py	100% <0%> (ø)	⬆️
rest_framework_json_api/django_filters/backends.py	100% <0%> (ø)	⬆️
... and 9 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 5650bd1...7e3c2da. Read the comment docs.

[sliverc]

Closing this PR as there hasn't been any progress and I don't quite see how this approach will work with relationships.

Please feel free to comment also in #155 for any suggestions how to move forward.