tests: add error prefix for json schema in checks

lib/build-clan/interface.nix

@@ -10,6 +10,11 @@ let
 in
 {
   options = {
+    _prefix = lib.mkOption {
+      type = types.listOf types.str;
+      internal = true;
+      default = [ ];
+    };
     self = lib.mkOption {
       type = types.raw;
       default = self;

lib/build-clan/module.nix

@@ -44,6 +44,7 @@ let
     buildInventory {
       inherit inventory directory;
       flakeInputs = config.self.inputs;
+      prefix = config._prefix ++ [ "inventoryClass" ];
     }
   );