public Collection<JID> getReplyRooms() {
        return Collections.unmodifiableCollection(replyRooms);
    }
Adds a new roster group that is allowed to subscribe and retrieve items.
The new roster group is not going to be added to the database. Instead it is just
kept in memory.

@param groupName the new roster group that is allowed to subscribe and retrieve items.
xmppserver/src/main/java/org/jivesoftware/openfire/pubsub/Node.java