Logic to handle optional_extra in Vision Excel converter input

[Jerry-Jinfeng-Guo]

Closes #338

In this PR:

• Logic to handle optional_extra
• Documentation
• Test

[Copilot]

Pull request overview

This PR implements logic to handle optional extra columns in the tabular converter, addressing issue #338. The feature allows specifying columns that should be included in extra_info if present but won't cause conversion failure if missing.

Key Changes:

• Added allow_missing parameter throughout the column definition parsing chain to support optional columns
• Implemented optional_extra wrapper in column definitions to mark columns as optional
• Enhanced error handling to gracefully skip missing optional columns while preserving required column behavior

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
src/power_grid_model_io/converters/tabular_converter.py	Core implementation of optional_extra logic with allow_missing parameter propagation and empty DataFrame handling for missing columns
tests/unit/converters/test_tabular_converter.py	Comprehensive test coverage for optional_extra feature including edge cases and integration tests
docs/converters/vision_converter.md	Documentation explaining optional_extra syntax, behavior, and use cases for Vision Excel exports

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[Copilot]

Pull request overview

Copilot reviewed 10 out of 13 changed files in this pull request and generated 2 comments.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
94.1% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud