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/event.ts

@@ -6,7 +6,7 @@ import { Models } from '../../models';
 import { SubscriptionPlan } from './types';
 
 @Injectable()
-export class QuotaOverride {
+export class PaymentEventHandlers {
   constructor(
     private readonly workspace: WorkspaceService,
     private readonly models: Models,

packages/backend/server/src/plugins/payment/index.ts

@@ -11,13 +11,13 @@ import { UserModule } from '../../core/user';
 import { WorkspaceModule } from '../../core/workspaces';
 import { StripeWebhookController } from './controller';
 import { SubscriptionCronJobs } from './cron';
+import { PaymentEventHandlers } from './event';
 import { LicenseController } from './license/controller';
 import {
   SelfhostTeamSubscriptionManager,
   UserSubscriptionManager,
   WorkspaceSubscriptionManager,
 } from './manager';
-import { QuotaOverride } from './quota';
 import {
   SubscriptionResolver,
   UserSubscriptionResolver,
@@ -49,7 +49,7 @@ import { StripeWebhook } from './webhook';
     SelfhostTeamSubscriptionManager,
     SubscriptionCronJobs,
     WorkspaceSubscriptionResolver,
-    QuotaOverride,
+    PaymentEventHandlers,
   ],
   controllers: [StripeWebhookController, LicenseController],
 })

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);
+    }
+  }
 }