private static <T> Map<String, T> without(String removed, Map<String, T> map) {
        Map<String, T> modified = new HashMap<>(map);
        modified.remove(removed);
        return Map.copyOf(modified);
    }
Reindexing status common to an application, one of its clusters, or a single document type in a cluster.
configserver/src/main/java/com/yahoo/vespa/config/server/application/ApplicationReindexing.java