docs: correct example for RouteReuseStrategy getRouteKey

Update the example to properly demonstrate the getRouteKey method usage fixes #65021

adev/src/content/guide/routing/customizing-route-behavior.md

@@ -160,12 +160,12 @@ The `RouteReuseStrategy` class provides five methods that control the lifecycle
 The following example demonstrates a custom route reuse strategy that selectively preserves component state based on route metadata:
 
 ```ts
-import { RouteReuseStrategy, ActivatedRouteSnapshot, DetachedRouteHandle } from '@angular/router';
+import { RouteReuseStrategy, Route, ActivatedRouteSnapshot, DetachedRouteHandle } from '@angular/router';
 import { Injectable } from '@angular/core';
 
 @Injectable()
 export class CustomRouteReuseStrategy implements RouteReuseStrategy {
-  private handlers = new Map<string, DetachedRouteHandle>();
+  private handlers = new Map<Route | null, DetachedRouteHandle>();
 
   shouldDetach(route: ActivatedRouteSnapshot): boolean {
     // Determines if a route should be stored for later reuse
@@ -197,12 +197,14 @@ export class CustomRouteReuseStrategy implements RouteReuseStrategy {
     return future.routeConfig === curr.routeConfig;
   }
 
-  private getRouteKey(route: ActivatedRouteSnapshot): string {
-    return route.routeConfig ?? '';
+  private getRouteKey(route: ActivatedRouteSnapshot): Route | null {
+    return route.routeConfig;
   }
 }
 ```
 
+NOTE: Avoid using the route path as the key when `canMatch` guards are involved, as it may lead to duplicate entries.
+
 ### Configuring a route to use a custom route reuse strategy
 
 Routes can opt into reuse behavior through route configuration metadata. This approach keeps the reuse logic separate from component code, making it easy to adjust behavior without modifying components: