public void addServerFeature(String namespace) {
        if (localServerFeatures.add(namespace)) {
            Lock lock = serverFeatures.getLock(namespace);
            lock.lock();
            try {
                HashSet<NodeID> nodeIDs = serverFeatures.get(namespace);
                if (nodeIDs == null) {
                    nodeIDs = new HashSet<>();
                }
                nodeIDs.add(XMPPServer.getInstance().getNodeID());
                serverFeatures.put(namespace, nodeIDs);
            }
            finally {
                lock.unlock();
            }
        }
    }
Adds one specific feature to the information returned whenever a disco for information is
made against the server.

@param namespace the namespace identifying the new server feature.
xmppserver/src/main/java/org/jivesoftware/openfire/disco/IQDiscoInfoHandler.java