Remove DataSourceService and clean up datasource migration logic (#19532)

## Summary

- **Drop the `objectMetadata.dataSourceId` foreign key and index** via a
1-22 fast instance command — column kept nullable for data preservation
- **Delete `DataSourceService`, `DataSourceModule`, and
`DataSourceException`** — all code now uses `workspace.databaseSchema`
directly
- **Remove `IS_DATASOURCE_MIGRATED` feature flag** from default flags
and all branching logic
- **Simplify workspace/object creation pipelines** —
`WorkspaceManagerService`, `DevSeederService`, and the object creation
action handler no longer route through `DataSourceService`
- **Keep `DataSourceEntity` and the `dataSource` table** for historical
data — entity stripped of all ORM relations

packages/twenty-server/src/database/commands/upgrade-version-command/instance-commands.constant.ts

@@ -7,6 +7,7 @@ import { AddPermissionFlagRoleIdIndexFastInstanceCommand } from 'src/database/co
 import { AddWorkspaceIdToIndirectEntitiesFastInstanceCommand } from 'src/database/commands/upgrade-version-command/1-22/1-22-instance-command-fast-1775758621017-add-workspace-id-to-indirect-entities';
 import { BackfillWorkspaceIdOnIndirectEntitiesSlowInstanceCommand } from 'src/database/commands/upgrade-version-command/1-22/1-22-instance-command-slow-1775758621018-backfill-workspace-id-on-indirect-entities';
 import { AddWorkspaceIdIndexesAndFksFastInstanceCommand } from 'src/database/commands/upgrade-version-command/1-22/1-22-instance-command-fast-1775761294897-add-workspace-id-indexes-and-fks-to-indirect-entities';
+import { DropObjectMetadataDataSourceFkFastInstanceCommand } from 'src/database/commands/upgrade-version-command/1-22/1-22-instance-command-fast-1775804361516-drop-object-metadata-data-source-fk';
 
 export const INSTANCE_COMMANDS = [
   AddViewFieldGroupIdIndexOnViewFieldFastInstanceCommand,
@@ -16,4 +17,5 @@ export const INSTANCE_COMMANDS = [
   AddWorkspaceIdToIndirectEntitiesFastInstanceCommand,
   BackfillWorkspaceIdOnIndirectEntitiesSlowInstanceCommand,
   AddWorkspaceIdIndexesAndFksFastInstanceCommand,
+  DropObjectMetadataDataSourceFkFastInstanceCommand,
 ];