Function backup 

pub async fn backup(
    infra: &InfraContext<'_>,
    token: &str,
    bos: Option<&str>,
    destination: Option<&str>,
) -> Result<(), Error>

Export BOS session templates (and related artifacts) to backup files.

Thin forwarder; authorization (admin-only) and filesystem path confinement are enforced by the caller before this function is invoked.