feat(copyparty): add read-only root volume

configs/nixos/guests/copyparty.nix

@@ -24,6 +24,12 @@ let
         description = "Copyparty access map from permission string to account names.";
       };
 
+      readOnly = lib.mkOption {
+        type = lib.types.bool;
+        default = false;
+        description = "Serve this Copyparty volume read-only.";
+      };
+
       flags = lib.mkOption {
         type = lib.types.listOf lib.types.str;
         default = [ ];
@@ -94,7 +100,7 @@ in
           inherit (cfg.reverseProxy) trustedSources;
         };
         volumes = lib.mapAttrs (_urlPath: volume: {
-          inherit (volume) path access flags;
+          inherit (volume) path access flags readOnly;
         }) cfg.volumes;
       };