protected void addConfigId(String id) {
        if (id == null) throw new NullPointerException("Config ID cannot be null.");
        getRoot().addDescendant(id, this);
        if (!isVespa() && (getVespa() != null))
            getVespa().addDescendant(this);
    }
Sets the config id for this producer. Will also add this
service to the root node, so the new config id will be picked
up.  Note that this producer will be known with both the old
and the new config id in the root node after using this method.
config-model/src/main/java/com/yahoo/config/model/producer/AnyConfigProducer.java