@Override
    public String toString() {
        return "id:" + namespace + ":" + documentType + ":" +
               (number.isPresent() ? "n=" + number.getAsLong() : group.map("g="::concat).orElse("")) +
               ":" + userSpecific;
    }
Represents a Vespa document id

@author jonmv
vespa-feed-client-api/src/main/java/ai/vespa/feed/client/DocumentId.java