Multi-words relation names error pointers are misformed

[leo-naeka]

Description of the Bug Report

#986 fixed #413 but did not covered multiple words in relations names.

Therefore, when fields names formatting is enforced, pointers still refers to /attributes/ since inflection breaks field identification as a relationship.

A PR with the failing tests and the fix are on the way.

Checklist

• Certain that this is a bug (if unsure or you have a question use discussions instead)
• Code snippet or unit test added to reproduce bug