Delete Bulk Action on Snippets does not respect "on_delete=models.PROTECT" on "ForeignKeys"

[LCMJ21]

Issue Summary

If a model is registered as a Snippet, and it has a ForeignKey that has the attribute on_delete=models.PROTECT, the Delete Bulk Action will not respect this condition.

Steps to Reproduce

1. Create a model that has a models.ForeignKey with the property on_delete=models.PROTECT.
2. Add a wagtail_hooks.py and register a SnippetViewSet of that model.
3. Use Delete Bulk Action

Technical details

• Django version: 5.0.3
• Wagtail version: 6.0.1
• Browser version: You can use Chrome 123 to find this out.