*/
    static <T> Key<T> key(Class<T> clazz) {
        return new Key<>(clazz, clazz);
    }

    /**
     * Create a key using the given class and id.
     */
    static <T> Key<T> key(Class<T> clazz, Object id) {
        return new Key<>(clazz, id);
    }

    /**
     * Key used to query the session data