Ensured that sparse fields only applies when rendering not when parsing

[sliverc]

Fixes #1216
Fixes #332

Description of the Change

The rendering of objects is flawed as the DJA renderer does most of the serialization again which should actually only be done by the serializer. Even though I reduced the readable fields in the serializer when sparse fields is used, it did not work.

I already adjusted extract_attributes that it uses the fields provided by the serializer. To adjust extract_relationships is more complex. Therefore, to get this critical issue fixed I also added code to exclude fields in the renderer when sparse fields is used.

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]

Codecov does not pass as it highlights two lines which I did change in this pull request but only changing the import not the functionality. There was no test for these lines before. I would say we ignore it, but I am open to revert the change to clean up the utils import in the renderer.