Ref #26 -- Add a regression test regarding overriding FK

[amureki]

Describe the change
I guess, I accidentally fixed this long ago, just never added a regression test, shame on me.

PR Checklist

• Change is covered with tests
• CHANGELOG.md is updated if needed

Summary by CodeRabbit

• Tests
  • Added regression test coverage to ensure that setting foreign key relationships to None does not inadvertently create phantom related objects in the system.

_{✏️ Tip: You can customize this high-level summary in your review settings.}

[coderabbitai]

📝 Walkthrough

Walkthrough

A regression test is added to verify that explicitly setting a foreign key field to None during recipe instance creation does not create phantom related model objects.

Changes

Cohort / File(s)	Summary
Test Regression tests/test_recipes.py	Added DummyNullFieldsModel to imports and introduced test_do_not_create_related_model_when_set_to_none regression test to verify that null-assigned foreign keys do not instantiate phantom related objects

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

Poem

🐰✨ When None is set, no phantom appears,
Our test chases away phantom fears,
A foreign key tamed with care,
Proves related models won't snare—
Recipe magic, crystal and clear! 🌟

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The PR title clearly and specifically describes the main change: adding a regression test for overriding foreign keys, with a reference to the related issue.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing touches

• 📝 Generate docstrings

---

_{Comment @coderabbitai help to get the list of available commands and usage tips.}