Function set_number_scheme 

pub async fn set_number_scheme(
    pool: &PgPool,
    actor: &Actor,
    id: Uuid,
    raw: &str,
) -> AppResult<Project>

Sets the numbering scheme of a project group (managers and admins); an empty scheme returns to the built-in {TYPE}-{SEQ:6}. Existing item numbers never change.

Invariants

• Permission: the group is visible to the actor (“not found” otherwise) and the actor manages it (or is an administrator; 403).
• Locks: the group row (FOR UPDATE).
• Audit: project.numbering (scheme before and after).
• Notifications / webhooks: none.
• Atomic: one transaction.