impl SledAgentUpdateStatus {
    /// Update status suitable for a given sled ID that isn't present in
    /// inventory.
    pub fn unknown(sled_id: SledUuid) -> Self {
        Self {
            sled_id,
            zones: IdOrdMap::new(),
            host_phase_2: HostPhase2Status {
                boot_disk: Err("unknown".to_string()),
                slot_a_version: TufRepoVersion::Unknown,
                slot_b_version: TufRepoVersion::Unknown,
            },
        }
    }
}