public static String format(String key, Object... params) {
        if (RESOURCE_BUNDLE.containsKey(key)) {
            String msg = RESOURCE_BUNDLE.getString(key);
            return MessageFormat.format(msg, params);
        } else {
            return MessageFormat.format("!!{0}!!", key);
        }
    }
Look up a message in the i18n resource message bundle by key, then format the
message with the given params and return the result.

@param key    the key
@param params the parameters
@return formatted string
gateway/platforms/vertx3/vertx3/src/main/java/io/apiman/gateway/platforms/vertx3/i18n/Messages.java