* The value is, e.g. fess_config <br>
     * comment: Index name for configuration data.
     * @return The value of found property. (NotNull: if not found, exception but basically no way)
     */
    String getIndexConfigIndex();

    /**
     * Get the value for the key 'index.user.index'. <br>
     * The value is, e.g. fess_user <br>
     * comment: Index name for user data.