@Override
    public void initialize(XMPPServer server) {
        super.initialize(server);
        serverName = server.getServerInfo().getXMPPDomain();
        rosterManager = server.getRosterManager();
    }
Handler of IQ packets whose child element is "sharedgroup" with namespace
"http://www.jivesoftware.org/protocol/sharedgroup". This handler will return the list of
shared groups where the user sending the request belongs.

@author Gaston Dombiak
xmppserver/src/main/java/org/jivesoftware/openfire/handler/IQSharedGroupHandler.java