refactor: delete dependent userconnection resources when an user is deleted (#3640)

#### What type of PR is this?
/kind improvement
/area core
/milestone 2.4.0

#### What this PR does / why we need it:
当用户被删除时关联删除用户的绑定账号信息

how to test it?
1. 创建用户
2. 绑定账号
3. 使用管理员删除此用户并查看关联的 UserConnection 是否被删除
```shell
curl -u 'your-username:your-password' http://127.0.0.1:8090/apis/auth.halo.run/v1alpha1/userconnections | jq  -r '.'
```
#### Which issue(s) this PR fixes:
Fixes #3639

#### Does this PR introduce a user-facing change?
```release-note
None
```

application/src/main/java/run/halo/app/core/extension/reconciler/UserReconciler.java

@@ -1,13 +1,15 @@
 package run.halo.app.core.extension.reconciler;
 
 import java.util.HashSet;
+import java.util.List;
 import java.util.Set;
 import lombok.AllArgsConstructor;
 import lombok.extern.slf4j.Slf4j;
 import org.apache.commons.lang3.StringUtils;
-import org.springframework.context.ApplicationEventPublisher;
+import org.springframework.retry.support.RetryTemplate;
 import org.springframework.stereotype.Component;
 import run.halo.app.core.extension.User;
+import run.halo.app.core.extension.UserConnection;
 import run.halo.app.extension.ExtensionClient;
 import run.halo.app.extension.controller.Controller;
 import run.halo.app.extension.controller.ControllerBuilder;
@@ -23,8 +25,12 @@ import run.halo.app.infra.utils.PathUtils;
 public class UserReconciler implements Reconciler<Request> {
     private static final String FINALIZER_NAME = "user-protection";
     private final ExtensionClient client;
-    private final ApplicationEventPublisher eventPublisher;
     private final ExternalUrlSupplier externalUrlSupplier;
+    private final RetryTemplate retryTemplate = RetryTemplate.builder()
+        .maxAttempts(20)
+        .fixedBackoff(300)
+        .retryOn(IllegalStateException.class)
+        .build();
 
     @Override
     public Result reconcile(Request request) {
@@ -85,6 +91,10 @@ public class UserReconciler implements Reconciler<Request> {
 
     private void cleanUpResourcesAndRemoveFinalizer(String userName) {
         client.fetch(User.class, userName).ifPresent(user -> {
+            // wait for dependent resources to be deleted
+            deleteUserConnections(userName);
+
+            // remove finalizer
             if (user.getMetadata().getFinalizers() != null) {
                 user.getMetadata().getFinalizers().remove(FINALIZER_NAME);
             }
@@ -92,6 +102,22 @@ public class UserReconciler implements Reconciler<Request> {
         });
     }
 
+    void deleteUserConnections(String userName) {
+        listConnectionsByUsername(userName).forEach(client::delete);
+        // wait for user connection to be deleted
+        retryTemplate.execute(callback -> {
+            if (listConnectionsByUsername(userName).size() > 0) {
+                throw new IllegalStateException("User connection is not deleted yet");
+            }
+            return null;
+        });
+    }
+
+    List<UserConnection> listConnectionsByUsername(String username) {
+        return client.list(UserConnection.class,
+            connection -> connection.getSpec().getUsername().equals(username), null);
+    }
+
     @Override
     public Controller setupWith(ControllerBuilder builder) {
         return builder