- Add language as a default attribute key in environment creation
- Create data migration to add language attribute key to existing environments
- Update tests to verify language is treated like other default attributes
- Fixes issue where CSV columns with 'Language' (capital L) would create duplicate custom attributes
The existing isStringMatch() function already handles case-insensitive matching,
so this change ensures language is properly matched alongside userId, email,
firstName, and lastName without any hardcoding in the UI layer.