Function approver_set_fingerprint 

pub fn approver_set_fingerprint(approvers: &[String]) -> String

SHA-256 hex fingerprint of a configured approver set.

The approver set comes from each broker’s own broker.toml, so two brokers can legitimately disagree during a rolling config change. Every break-glass audit event records this fingerprint, which makes the disagreement visible after the fact.

The input is sorted and de-duplicated first, and each name is length-prefixed, so the fingerprint depends on the members alone: not on the order an operator wrote them in, and not on where one name ends and the next begins.