Function guardian_notifications 

pub fn guardian_notifications(
    flags: &[Flag],
    asset_uri: &str,
    guardian_did: &str,
    principal_did: &str,
    min_severity: FlagSeverity,
    now_unix: u64,
) -> Vec<GuardianNotification>

Produce guardian notifications for the flags that meet or exceed min_severity. Pure — the caller (host) records each to the ledger and delivers it. A principal not under guardianship yields none (the caller passes no guardian).