fix: overwrite or unset unknown cookie locale

[BobbieGoede]

🔗 Linked issue

• Cookie Value Error #2822

❓ Type of change

• 📖 Documentation (updates to the documentation, readme or JSdoc annotations)
• 🐞 Bug fix (a non-breaking change that fixes an issue)
• 👌 Enhancement (improving an existing functionality like performance)
• ✨ New feature (a non-breaking change that adds functionality)
• 🧹 Chore (updates to the build process or auxiliary tools and libraries)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

📚 Description

Resolves #2822

This changes the cookie behavior, if the cookie locale is set to something truthy but does not match a locale it will be overwritten to the configured defaultLocale or undefined if no default has been set.

The only real use case I can imagine is when websites remove locales or when they update a locale code, this would lead to unexpected behaviour.

📝 Checklist

• I have linked an issue or discussion.
• I have added tests (if possible).
• I have updated the documentation accordingly.

[kazupon]

LGTM!