/** The key of the configuration. e.g. 0-1 */
    String INDEX_auto_expand_replicas = "index.auto_expand_replicas";

    /** The key of the configuration. e.g. SHA-512 */
    String INDEX_ID_DIGEST_ALGORITHM = "index.id.digest.algorithm";

    /** The key of the configuration. e.g. admin */
    String INDEX_USER_initial_password = "index.user.initial_password";