Function claim_effect 

pub fn claim_effect(
    intent: &DispatchIntent,
    existing: Option<&ClaimLease>,
    progress: EffectProgress,
    owner: &str,
    now_unix_ms: i64,
    lease_until_unix_ms: i64,
) -> ClaimVerdict

Take the claim for one dispatch intent, or report why it cannot be taken.

The only clock input is the persisted lease expiry. No argument describes the previous host process, so an unexpired claim held by a dead process is still ClaimVerdict::Held.