nixos/meilisearch: add instructions for generating masterKeyFile

        Path to file which contains the master key.

        By doing so, all routes will be protected and will require a key to be accessed.

        If no master key is provided, all routes can be accessed without requiring any key.

        You can generate a master key by running `openssl rand -base64 36`.

        Alternatively, you can start Meilisearch without a master key and use the pre-generated key from the service's logs that can be obtained by `journalctl -u meilisearch | grep -- --master-key`.

      '';

      default = null;

      type = lib.types.nullOr lib.types.path;