Deprecate dataSource table with dual-write to workspace.databaseSchema (#19059)

## Summary
- Starts deprecation of the `core.dataSource` table by introducing a
dual-write system: `DataSourceService.createDataSourceMetadata` now
writes to both `core.dataSource` and `core.workspace.databaseSchema`
- Migrates read sites (`WorkspaceDataSourceService.checkSchemaExists`,
`WorkspaceSchemaFactory`, `MiddlewareService`,
`WorkspacesMigrationCommandRunner`) to read from
`workspace.databaseSchema` instead of querying the `dataSource` table
- Removes the unused `databaseUrl` field from `WorkspaceEntity` and
drops the column via migration
- Adds a 1.20 upgrade command to backfill `workspace.databaseSchema`
from `dataSource.schema` for existing workspaces

packages/twenty-server/src/engine/middlewares/middleware.module.ts

@@ -1,6 +1,7 @@
 import { Module } from '@nestjs/common';
 
 import { TokenModule } from 'src/engine/core-modules/auth/token/token.module';
+import { FeatureFlagModule } from 'src/engine/core-modules/feature-flag/feature-flag.module';
 import { JwtModule } from 'src/engine/core-modules/jwt/jwt.module';
 import { DataSourceModule } from 'src/engine/metadata-modules/data-source/data-source.module';
 import { WorkspaceManyOrAllFlatEntityMapsCacheModule } from 'src/engine/metadata-modules/flat-entity/services/workspace-many-or-all-flat-entity-maps-cache.module';
@@ -10,6 +11,7 @@ import { WorkspaceCacheStorageModule } from 'src/engine/workspace-cache-storage/
 @Module({
   imports: [
     DataSourceModule,
+    FeatureFlagModule,
     WorkspaceCacheStorageModule,
     WorkspaceManyOrAllFlatEntityMapsCacheModule,
     TokenModule,