public static String getString(String key) {
        try {
            return RESOURCE_BUNDLE.getString(key);
        } catch (MissingResourceException e) {
            return '!' + key + '!';
        }
    }
Gets a string from the bundle.
@param key the key
@return the resolved string or !key! if missing
manager/api/security/src/main/java/io/apiman/manager/api/security/i18n/Messages.java