Deprecate object metadata maps in favor of flat entities (#16080)

## Context
Deprecating the old objectMetadataMap type in favour of split flat
entities to match with our new caching.
In the long run, trying to achieve:
- Better performance through caching
- Consistent data access patterns across the codebase
- Reduced database queries

Now that everything is based on flat entities, which are cached, we can
finish the refactoring of workspace context cache which should already
improve performances.
Then the last step will be to consume that new cache in the new global
datasource to get rid of the many workspace datasources stored in the
server

packages/twenty-server/src/engine/workspace-manager/dev-seeder/data/services/dev-seeder-data.service.ts

@@ -8,8 +8,9 @@ import { DataSource } from 'typeorm';
 
 import { FeatureFlagKey } from 'src/engine/core-modules/feature-flag/enums/feature-flag-key.enum';
 import { FileStorageService } from 'src/engine/core-modules/file-storage/file-storage.service';
+import { WorkspaceManyOrAllFlatEntityMapsCacheService } from 'src/engine/metadata-modules/flat-entity/services/workspace-many-or-all-flat-entity-maps-cache.service';
+import { FlatObjectMetadata } from 'src/engine/metadata-modules/flat-object-metadata/types/flat-object-metadata.type';
 import { ObjectMetadataServiceV2 } from 'src/engine/metadata-modules/object-metadata/object-metadata-v2.service';
-import { ObjectMetadataEntity } from 'src/engine/metadata-modules/object-metadata/object-metadata.entity';
 import { type WorkspaceEntityManager } from 'src/engine/twenty-orm/entity-manager/workspace-entity-manager';
 import { computeTableName } from 'src/engine/utils/compute-table-name.util';
 import {
@@ -268,6 +269,7 @@ export class DevSeederDataService {
     private readonly objectMetadataService: ObjectMetadataServiceV2,
     private readonly timelineActivitySeederService: TimelineActivitySeederService,
     private readonly fileStorageService: FileStorageService,
+    private readonly flatEntityMapsCacheService: WorkspaceManyOrAllFlatEntityMapsCacheService,
   ) {}
 
   public async seed({
@@ -282,6 +284,14 @@ export class DevSeederDataService {
     const objectMetadataItems =
       await this.objectMetadataService.findManyWithinWorkspace(workspaceId);
 
+    const { flatObjectMetadataMaps, flatFieldMetadataMaps } =
+      await this.flatEntityMapsCacheService.getOrRecomputeManyOrAllFlatEntityMaps(
+        {
+          workspaceId,
+          flatMapsKeys: ['flatObjectMetadataMaps', 'flatFieldMetadataMaps'],
+        },
+      );
+
     await this.coreDataSource.transaction(
       async (entityManager: WorkspaceEntityManager) => {
         await this.seedRecordsInBatches({
@@ -300,7 +310,12 @@ export class DevSeederDataService {
 
         await this.seedAttachmentFiles(workspaceId);
 
-        await prefillWorkflows(entityManager, schemaName, objectMetadataItems);
+        await prefillWorkflows(
+          entityManager,
+          schemaName,
+          flatObjectMetadataMaps,
+          flatFieldMetadataMaps,
+        );
       },
     );
   }
@@ -316,7 +331,7 @@ export class DevSeederDataService {
     schemaName: string;
     workspaceId: string;
     featureFlags?: Record<FeatureFlagKey, boolean>;
-    objectMetadataItems: ObjectMetadataEntity[];
+    objectMetadataItems: FlatObjectMetadata[];
   }) {
     const batches = getRecordSeedsBatches(workspaceId, featureFlags);