public void addUserItemsProvider( UserItemsProvider provider )
    {
        this.userItemsProviders.add( provider );
    }
Adds the items provided by the new service that implements the UserItemsProvider interface. This information will
be used whenever a disco for items is made against users of the server.

@param provider the UserItemsProvider that provides new user items.
xmppserver/src/main/java/org/jivesoftware/openfire/disco/IQDiscoItemsHandler.java