* The value is, e.g. ja <br>
     * comment: Supported languages for online help.
     * @return The value of found property. (NotNull: if not found, exception but basically no way)
     */
    String getOnlineHelpSupportedLangs();

    /**
     * Get the value for the key 'forum.link'. <br>
     * The value is, e.g. https://discuss.codelibs.org/c/Fess{lang}/ <br>
     * comment: Forum link for user support.