@Override
    public final boolean addUserConfig(ConfigInstance.Builder builder) {
        boolean didApply = false;
        if (parent != null) {
            didApply = parent.addUserConfig(builder);
        }

        log.log(Level.FINEST, () -> "User configs is: " + userConfigs.toString());
        // TODO: What do we do with md5. Currently ignored for user configs?
        ConfigDefinitionKey key = new ConfigDefinitionKey(builder.getDefName(), builder.getDefNamespace());
        if (userConfigs.get(key) != null) {
            log.log(Level.FINEST, () -> "Apply in " + configId);
            applyUserConfig(builder, userConfigs.get(key));
            didApply = true;
        }
        return didApply;
    }
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