void finishSnapshot() {
        for (Entry<Uuid, StandardAcl> entry : image.acls().entrySet()) {
            if (!changes.containsKey(entry.getKey())) {
                changes.put(entry.getKey(), Optional.empty());
            }
        }
    }
Returns a Map of deltas from ACL ID to optional StandardAcl. An empty optional value indicates the ACL
is for removal. An optional with a value indicates the ACL is to be added.

@return Map of deltas.
metadata/src/main/java/org/apache/kafka/image/AclsDelta.java