Add draft error doc

refs #17235
Add error doc to planning tree
Change tests from "updated" to "modified"
Change "updated" to "modified"
Convert /products/<id> to serializer. Not done -- field names?
Merge branch 'enhancement/17331' of github.com:osu-cass/whats-fresh-api into enhancement/17331

Conflicts:
	whats_fresh/whats_fresh_api/tests/views/test_product_detail_view.py