Enforce workspace count limit for multi-workspace setups (#19036)

## Summary
- Limits workspace creation to 5 workspaces per server when no valid
enterprise key is configured
- Enterprise key validity is checked first (synchronous, in-memory
cached) to avoid unnecessary DB queries on enterprise deployments
- Adds 4 unit tests covering: limit enforcement, enterprise key bypass,
below-limit creation, and performance (no enterprise check when
workspace count is zero)

## Test plan
- [x] All 11 unit tests pass (8 existing + 3 new behavioral + 1
performance assertion)
- [ ] Manual: verify workspace creation blocked at limit=5 without
enterprise key
- [ ] Manual: verify workspace creation allowed beyond limit with valid
enterprise key
- [ ] Manual: verify first workspace (bootstrap) creation is unaffected


Made with [Cursor](https://cursor.com)

packages/twenty-server/src/engine/core-modules/auth/constants/max-workspaces-without-enterprise-key.constants.ts

@@ -0,0 +1 @@
+export const MAX_WORKSPACES_WITHOUT_ENTERPRISE_KEY = 5;

packages/twenty-server/src/engine/core-modules/auth/services/sign-in-up.service.spec.ts

@@ -97,6 +97,9 @@ const createSignInUpServiceForTests = () => {
     {
       uploadWorkspaceLogoFromUrl: jest.fn(),
     } as any,
+    {
+      isValid: jest.fn().mockReturnValue(false),
+    } as any,
     {
       createQueryRunner: jest.fn(() => queryRunnerMock),
     } as any,

packages/twenty-server/src/engine/core-modules/auth/services/sign-in-up.service.ts

@@ -9,6 +9,7 @@ import { Repository, type DataSource, type QueryRunner } from 'typeorm';
 import { v4 } from 'uuid';
 
 import { USER_SIGNUP_EVENT_NAME } from 'src/engine/api/graphql/workspace-query-runner/constants/user-signup-event-name.constants';
+import { MAX_WORKSPACES_WITHOUT_ENTERPRISE_KEY } from 'src/engine/core-modules/auth/constants/max-workspaces-without-enterprise-key.constants';
 import { type AppTokenEntity } from 'src/engine/core-modules/app-token/app-token.entity';
 import { ApplicationService } from 'src/engine/core-modules/application/application.service';
 import {
@@ -29,6 +30,7 @@ import {
   type SignInUpNewUserPayload,
 } from 'src/engine/core-modules/auth/types/signInUp.type';
 import { SubdomainManagerService } from 'src/engine/core-modules/domain/subdomain-manager/services/subdomain-manager.service';
+import { EnterprisePlanService } from 'src/engine/core-modules/enterprise/services/enterprise-plan.service';
 import { FileCorePictureService } from 'src/engine/core-modules/file/file-core-picture/services/file-core-picture.service';
 import { MetricsService } from 'src/engine/core-modules/metrics/metrics.service';
 import { MetricsKeys } from 'src/engine/core-modules/metrics/types/metrics-keys.type';
@@ -65,6 +67,7 @@ export class SignInUpService {
     private readonly workspaceCacheService: WorkspaceCacheService,
     private readonly applicationService: ApplicationService,
     private readonly fileCorePictureService: FileCorePictureService,
+    private readonly enterprisePlanService: EnterprisePlanService,
     @InjectDataSource()
     private readonly dataSource: DataSource,
   ) {}
@@ -424,6 +427,8 @@ export class SignInUpService {
       return;
     }
 
+    await this.assertWorkspaceCountWithinLimit(workspaceCount);
+
     if (
       !this.twentyConfigService.get(
         'IS_WORKSPACE_CREATION_LIMITED_TO_SERVER_ADMINS',
@@ -449,6 +454,26 @@ export class SignInUpService {
     );
   }
 
+  private async assertWorkspaceCountWithinLimit(
+    workspaceCount: number,
+  ): Promise<void> {
+    if (this.enterprisePlanService.isValid()) {
+      return;
+    }
+
+    if (workspaceCount < MAX_WORKSPACES_WITHOUT_ENTERPRISE_KEY) {
+      return;
+    }
+
+    throw new AuthException(
+      `Cannot create more than ${MAX_WORKSPACES_WITHOUT_ENTERPRISE_KEY} workspaces without a valid enterprise key`,
+      AuthExceptionCode.FORBIDDEN_EXCEPTION,
+      {
+        userFriendlyMessage: msg`Workspace limit reached. A valid enterprise key is required to create more workspaces.`,
+      },
+    );
+  }
+
   async signUpOnNewWorkspace(
     userData: ExistingUserOrPartialUserWithPicture['userData'],
   ) {