Function install_expiry_times 

pub fn install_expiry_times(
    times: ExpiryTimes,
) -> Result<(), ExpiryTimesInstallError>

Install the process-wide expiry time policy. Call once at startup, before any component derives expiry timestamps.

Idempotent for identical configurations; installing a different configuration after the first install is an error because earlier-derived timestamps would silently disagree with later ones.