Restrict language destroy if nodes present

[tvdeyen]

What is this pull request for?

This dissallows to remove a language if menu nodes are still attached.

Also refactors existing checks into Rails built-ins by using dependent: :restrict_with_error
over a custom before_destroy hook.

Checklist

• I have followed Pull Request guidelines
• I have added a detailed description into each commit message
• I have added tests to cover this change

---

• To see the specific tasks where the Asana app for GitHub is being used, see below:
  • https://app.asana.com/0/0/1211257231387966

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.99%. Comparing base (05c7da2) to head (2d282fd).
⚠️ Report is 6 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3383      +/-   ##
==========================================
- Coverage   97.00%   96.99%   -0.01%     
==========================================
  Files         277      277              
  Lines        7271     7262       -9     
==========================================
- Hits         7053     7044       -9     
  Misses        218      218              

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