Doc metadata de type date

Ajouter les formats de date interprêtés: YYYY -> 1995 YYYY-MM -> 1995-02 YYYY-MM-DD -> 1995-02-16 YYYY(.*)month -> 1995, february YYYY-YYYY -> 1995-1996

Checklist

• https://wiki.teklia.com/en/arkindex/doc/models/meta-data
• https://arkindex.gitlab.io/api-client/#operation/CreateMetaData

Merge requests: !680 (merged).

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Imported from Trello