default Path getExternalMessageBundlesDir() {
        Path dir = getConfigDirectory().resolve("i18n");
        if (Files.notExists(dir)) {
            throw new MissingResourceException("External i18n resources missing", "i18n", dir.toString());
        }
        return dir;
    }
Resolve the configuration directory, this varies depending on the platform.
@return the public configuration directory
manager/ui/war/src/main/java/io/apiman/manager/ui/server/IUIConfig.java