nixos/moodle: use PHP 8.1

  mysqlLocal = cfg.database.createLocally && cfg.database.type == "mysql";

  pgsqlLocal = cfg.database.createLocally && cfg.database.type == "pgsql";

  phpExt = pkgs.php80.buildEnv {

  phpExt = pkgs.php81.buildEnv {

    extensions = { all, ... }: with all; [ iconv mbstring curl openssl tokenizer soap ctype zip gd simplexml dom intl sqlite3 pgsql pdo_sqlite pdo_pgsql pdo_odbc pdo_mysql pdo mysqli session zlib xmlreader fileinfo filter opcache exif sodium ];

    extraConfig = "max_input_vars = 5000";

  };