Function validate_and_prepare_time_alert 

pub fn validate_and_prepare_time_alert(
    name: &str,
    alert_time_ns: UnixNanos,
    allow_past: Option<bool>,
    ts_now: UnixNanos,
) -> Result<(Ustr, UnixNanos)>

Validates and normalizes parameters for a time alert.

allow_past defaults to true. When enabled, a past alert timestamp is replaced with ts_now. Returns the interned name and normalized alert timestamp.

Errors

Returns an error if name is invalid or the alert is in the past when past alerts are disallowed.