fix: Add reserved subdomains constant and update validation on generateSubdomain (#15217)

## Description

Fixes #15160 

- Moved the reserved subdomains to a separate shared constant file:
`packages/twenty-server/src/engine/core-modules/workspace/constants/reserved-subdomains.constant.ts`
- Updated the validation while generating subdomain to check if the
extracted subdomain (from email or display name) is reserved
- When a reserved subdomain is detected, the server will automatically
fall back to a random subdomain

---------

Co-authored-by: Naineel Soyantar <naineelsoyantar@gmail.com>
Co-authored-by: Charles Bochet <charles@twenty.com>

packages/twenty-server/src/engine/metadata-modules/route-trigger/route-trigger.module.ts

@@ -2,7 +2,7 @@ import { Module } from '@nestjs/common';
 import { TypeOrmModule } from '@nestjs/typeorm';
 
 import { AuthModule } from 'src/engine/core-modules/auth/auth.module';
-import { DomainManagerModule } from 'src/engine/core-modules/domain-manager/domain-manager.module';
+import { WorkspaceDomainsModule } from 'src/engine/core-modules/domain/workspace-domains/workspace-domains.module';
 import { WorkspaceManyOrAllFlatEntityMapsCacheModule } from 'src/engine/metadata-modules/flat-entity/services/workspace-many-or-all-flat-entity-maps-cache.module';
 import { RouteTriggerResolver } from 'src/engine/metadata-modules/route-trigger/resolvers/route-trigger.resolver';
 import { RouteTriggerController } from 'src/engine/metadata-modules/route-trigger/route-trigger.controller';
@@ -17,7 +17,7 @@ import { WorkspaceMigrationV2Module } from 'src/engine/workspace-manager/workspa
   imports: [
     TypeOrmModule.forFeature([RouteTrigger]),
     AuthModule,
-    DomainManagerModule,
+    WorkspaceDomainsModule,
     ServerlessFunctionModule,
     WorkspaceManyOrAllFlatEntityMapsCacheModule,
     WorkspaceMigrationV2Module,