Architecture & Design: rename file.folder_id into file.parent_id

[EdouardVanbelle]

Hello @DioCrafts , do you have any objection/recommendation to rename file.folder_id into file.parent_id (SQL, Structure and API)

This will permit a common Trait between File and Folder:
StorageItem trait with id(), name(), storage_path(), owner_id(), created_at(), modified_at(), parent_id() — lets share/search/batch code be generic instead of duplicating for each type.

Simplify add of new type (for example symlink in the future)
Simplify UI logic (I saw some if item.parent_id rather if item.type === "folder")

I guess doing that will require OxiCloud-Desktop to be adapted consequently (we can make a transition in 2 phase on API side)

no clue if other app, clients are using this key as it will be a breaking change

Any though ?