fix: use base class when reporting invalidLayerCode

Author: mcquenji

lib/src/rules/base_class_rule.dart

@@ -194,7 +194,7 @@ class _Visitor extends SimpleAstVisitor<void> {
     if (pathInfo.layer == null ||
         !baseInfo.allowedLayers.contains(pathInfo.layer)) {
       _reportWithCode(node.namePart, BaseClassRule.invalidLayerCode, [
-        className,
+        baseInfo.name,
         baseInfo.allowedLayersLabel,
       ]);
     }

test/rules/base_class_rule_test.dart

@@ -51,6 +51,7 @@ abstract class UserService extends Service {}
         code.indexOf('UserService'),
         'UserService'.length,
         name: 'base_class_invalid_layer',
+        messageContains: 'Classes extending Service must be defined',
       ),
     ]);
   }