boolean canModify(JID user) {
        return user.equals(getJID()) || user.toBareJID().equals(getOwner().toBareJID()) || node.getService().isServiceAdmin(user);
    }
Returns true if the specified user is allowed to modify or cancel the subscription. Users
that are allowed to modify/cancel the subscription are: the entity that is recieving the
notifications, the owner of the subscriptions or sysadmins of the pubsub service.

@param user the user that is trying to cancel the subscription.
@return true if the specified user is allowed to modify or cancel the subscription.
xmppserver/src/main/java/org/jivesoftware/openfire/pubsub/NodeSubscription.java