public static UserConfigRepo build(Element producerSpec, ConfigDefinitionStore configDefinitionStore, DeployLogger deployLogger) {
        Map<ConfigDefinitionKey, ConfigPayloadBuilder> builderMap = new LinkedHashMap<>();
        log.log(Level.FINE, () -> "getUserConfigs for " + producerSpec);
        for (Element configE : XML.getChildren(producerSpec, "config")) {
            buildElement(configE, builderMap, configDefinitionStore, deployLogger);
        }
        return new UserConfigRepo(builderMap);
    }
@Test
    void no_exception_when_config_class_does_not_exist() {
        Element configRoot = getDocument("<config name=\"is.unknown\">" +
                "    <foo>1</foo>" +
                "</config>");
        UserConfigRepo repo = UserConfigBuilder.build(configRoot, configDefinitionStore, new BaseDeployLogger());
        ConfigPayloadBuilder builder = repo.get(new ConfigDefinitionKey("unknown", "is"));
        assertNotNull(builder);
    }