feat(server): handle account deleting properly (#12399)

<!-- This is an auto-generated comment: release notes by coderabbit.ai -->
## Summary by CodeRabbit

- **New Features**
  - Users are now prevented from deleting their account if they own one or more team workspaces. A clear error message instructs users to transfer ownership or delete those workspaces first.
  - Disabled (banned) users are explicitly prevented from signing in or re-registering.
  - Added new error messages and translations to improve clarity around account deletion restrictions.

- **Bug Fixes**
  - Disabled users are now explicitly handled to prevent sign-in attempts.

- **Tests**
  - Introduced comprehensive end-to-end tests covering account deletion, banning, and re-registration scenarios.

- **Chores**
  - Improved event handling for user deletion and subscription cancellation.
  - Updated localization resources with new error messages.
  - Renamed payment event handler class for clarity.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/backend/server/src/plugins/payment/manager/user.ts

@@ -10,6 +10,7 @@ import {
   InternalServerError,
   InvalidCheckoutParameters,
   Mutex,
+  OnEvent,
   SubscriptionAlreadyExists,
   SubscriptionPlanNotFound,
   TooManyRequest,
@@ -683,4 +684,17 @@ export class UserSubscriptionManager extends SubscriptionManager {
       throw new Error('user should exists for stripe subscription or invoice.');
     }
   }
+
+  @OnEvent('user.deleted')
+  async onUserDeleted({ id }: Events['user.deleted']) {
+    const subscription = await this.db.subscription.findFirst({
+      where: {
+        targetId: id,
+      },
+    });
+
+    if (subscription?.stripeSubscriptionId) {
+      await this.stripe.subscriptions.cancel(subscription.stripeSubscriptionId);
+    }
+  }
 }