fix: change_items_per_page_url on paginator component

[Paul-Bob]

Description

Fixes #3667

Fixing change_items_per_page_url by using the parent resource's route key instead of the parent model's route key.

This is useful when the parent resource uses self.model_class and its route key differs from that of the parent model.

Checklist:

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works

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[github-actions]

This PR has been merged into main. The functionality will be available in the next release.

Please check the release guide for more information.