Migrate metadata cache (#16030)

## Context
Deprecating legacy ObjectMetadata from cache in favor of flat entities.
Introducing utils to build byName/byNameSingular/byNamePlural in
isolated cases

## Next
- I had to introduce a util to build from flat to legacy
objectMetadataMaps, we should instead use flat maps directly when needed
(datasource, schema generation, etc)
- Deprecate metadata version in the cache
- Use the new cache strategy for flat entities with permissions and
feature flags and inject in the global datasource context

packages/twenty-server/src/engine/metadata-modules/flat-field-metadata/utils/build-field-maps-for-object.util.ts

@@ -0,0 +1,45 @@
+import { isDefined } from 'twenty-shared/utils';
+
+import { type FlatEntityMaps } from 'src/engine/metadata-modules/flat-entity/types/flat-entity-maps.type';
+import { type FlatFieldMetadata } from 'src/engine/metadata-modules/flat-field-metadata/types/flat-field-metadata.type';
+import { isMorphOrRelationFlatFieldMetadata } from 'src/engine/metadata-modules/flat-field-metadata/utils/is-morph-or-relation-flat-field-metadata.util';
+
+export type FieldMapsForObject = {
+  fieldIdByName: Record<string, string>;
+  fieldIdByJoinColumnName: Record<string, string>;
+};
+
+export const buildFieldMapsForObject = (
+  flatFieldMetadataMaps: FlatEntityMaps<FlatFieldMetadata>,
+  objectMetadataId: string,
+): FieldMapsForObject => {
+  const fieldIdByName: Record<string, string> = {};
+  const fieldIdByJoinColumnName: Record<string, string> = {};
+
+  for (const [fieldId, field] of Object.entries(flatFieldMetadataMaps.byId)) {
+    if (!isDefined(field)) {
+      continue;
+    }
+
+    if (field.objectMetadataId !== objectMetadataId) {
+      continue;
+    }
+
+    fieldIdByName[field.name] = fieldId;
+
+    if (isMorphOrRelationFlatFieldMetadata(field)) {
+      const joinColumnName = (
+        field.settings as { joinColumnName?: string } | undefined
+      )?.joinColumnName;
+
+      if (joinColumnName) {
+        fieldIdByJoinColumnName[joinColumnName] = fieldId;
+      }
+    }
+  }
+
+  return {
+    fieldIdByName,
+    fieldIdByJoinColumnName,
+  };
+};