feat: add Detector interface (#478)

Author: Copilot

src/main/java/org/casbin/jcasbin/detector/Detector.java

@@ -0,0 +1,29 @@
+// Copyright 2025 The casbin Authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package org.casbin.jcasbin.detector;
+
+import org.casbin.jcasbin.rbac.RoleManager;
+
+/**
+ * Detector defines the interface of a policy consistency checker, currently used to detect RBAC inheritance cycles.
+ */
+public interface Detector {
+    /**
+     * Checks whether the current status of the passed-in RoleManager contains logical errors (e.g., cycles in role inheritance).
+     * @param rm RoleManager instance
+     * @return If an error is found, return a description message; otherwise return null
+     */
+    String check(RoleManager rm);
+}