Function cancel_checkout 

pub async fn cancel_checkout(
    pool: &PgPool,
    actor: &Actor,
    id: Uuid,
    reason: Option<&str>,
) -> AppResult<Revision>

Releases the edit lock without uploading anything (“cancel check-out”). Administrators may release locks of other users, managers of the item’s group those of users who are gone: no longer members (who cannot release them themselves once a restricted group hides the revision) or deactivated. A check-in with new file versions is files::check_in; the bulk release for one holder is checkouts::release_held.

Invariants

• Permission: CAD editor; the revision is visible (“not found” otherwise). Nothing happens when it is not checked out. Another user’s check-out may be released by an administrator, by a manager of the group when that user is no longer a member or is deactivated, or by a manager of the group for an active member with a reason (issue #173, step 6); 403 otherwise (a manager without a reason is told to give one).
• Data: a reason has RELEASE_REASON_MIN to RELEASE_REASON_MAX characters (400).
• Locks: the revision row (revisions::lock).
• Audit: revision.checkout_cancel; revision.checkout_forced_release when the check-out was held by someone else, with the reason.
• Notifications: on a forced release the former holder, with the reason; otherwise none.
• Webhooks: none.
• Atomic: one transaction.