Function set_retention 

pub async fn set_retention(
    pool: &PgPool,
    actor: &Actor,
    file_id: Uuid,
    retention: FileRetention,
) -> AppResult<FileRecord>

Chooses what happens to the old versions of a file: all keeps every version, latest lets the housekeeping remove the versions a newer one replaced (see services::retention::purge_superseded_versions).

Invariants

• Permission: the file is visible to the actor (“not found” otherwise), its revision is checked out by the actor (409 otherwise) and editable (revisions::ensure_editable: in work, CAD editor of its group).
• Locks: the revision row (revisions::lock) and the file row (FOR UPDATE).
• Audit: file.retention, only when the setting actually changes.
• Data: nothing is removed here; the removal is the housekeeping’s.
• Notifications / webhooks: none.
• Atomic: one transaction.