Update to JADNC v5.6.0

[bkoelman]

Replicated applicable changes from JsonApiDotNetCore up to v5.6.0.

QUALITY CHECKLIST

• [x] Changes implemented in code
• [x] Complies with our contributing guidelines
• [x] Adapted tests
• [ ] N/A: Documentation updated

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 95.02%. Comparing base (961ecef) to head (949b5b0).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #62 +/- ## ========================================== + Coverage 93.16% 95.02% +1.85% ========================================== Files 13 13 Lines 234 241 +7 Branches 36 36 ========================================== + Hits 218 229 +11 + Misses 9 7 -2 + Partials 7 5 -2 ```

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