# Description  
This PR introduces the `VersionedSet` class, a flexible and generic
solution for storing and retrieving multiple versions of data.

Initially applied to the `Millesime` enum class, this implementation
supports managing geographical formats tied to the COG (Official
Geographic Code).

# Key Changes  
- Added the `VersionedSet` class to handle versioned data.  
- Applied `VersionedSet` to the `Millesime` enum for geographical
formats.
- Refactored existing code to integrate the new versioning system.  
- Added tests to validate the new features.  

This refactor enhances flexibility and improves the maintainability of
the codebase by standardizing the handling of versioned data.

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Co-authored-by: Pierre Camilleri <22995923+pierrecamilleri@users.noreply.github.com>
Co-authored-by: Pierre Camilleri <pierre.camilleri@multi.coop>