Deprecate asExpression from field metadata search_vector (#22287)

## Summary

Fully deprecates the cached `asExpression` / `generatedType` settings on
`TS_VECTOR` (searchVector) fields. Previously the generated-column
expression was stored in `FieldMetadataSettings` and kept in sync via
imperative recompute side-effects. It is now **derived at DDL time**
from the `searchFieldMetadata` rows that describe which fields feed the
search vector, making `searchFieldMetadata` the single source of truth
and removing a whole class of cache-drift bugs.

This is delivered across the milestones tracked in #2587 and coordinates
with the frontend migration (#1428).

## Why

- The searchVector expression lived in two places (stored
`settings.asExpression` + the actual generated column), kept consistent
by bespoke side-effects (`recompute-search-vector-on-field-rename`,
label-identifier recompute, etc.).
- The frontend reconstructed the searchable-fields list by
**regex-parsing** the stored `asExpression`.
- Both are brittle. Deriving the expression from `searchFieldMetadata`
rows at build/run time removes the cache and the parsing.

## What changed

### Server - data model & derivation
- Introduce the `tsVectorFieldMetadata` relation on
`searchFieldMetadata` (`tsVectorFieldMetadataId` / universal identifier)
linking each searchable-field row to its target `TS_VECTOR` field.
- New runtime derivation
`deriveSearchVectorAsExpressionForTsVectorField`
(`flat-search-field-metadata/utils/...`) used by the create-object and
update-field handlers to generate the column expression from
`searchFieldMetadata` rows.
- Remove `asExpression` / `generatedType` from stored settings:
`FieldMetadataSettings.TS_VECTOR` is now `null`; the column builder
(`generate-column-definitions.util.ts`) hardcodes `generatedType:
'STORED'` and requires the derived expression.
- Delete the imperative recompute side-effects and the
`compute-search-vector-universal-settings-from-object-manifest` path;
drop the `settings` block from all 28 standard
`compute-*-standard-flat-field-metadata` utils.

### Server - migration runner
- New `rebuildSearchVector` marker on `update-field` actions: the
orchestrator synthesizes targeted column rebuilds
(`compute-search-vector-rebuild-target-universal-identifiers.util.ts` +
the deprioritize aggregator) only when a searchFieldMetadata change or
indexed-field rename actually requires it - instead of rebuilding on
every settings touch.
- Deferrable FKs + in-flight ID resolution so a `searchFieldMetadata`
row and its `TS_VECTOR` field can be created in the same transaction
(deterministic UUIDs).

### Frontend (contract change, #1428)
- New `SearchFieldMetadataDTO` + dataloader exposing
`searchFieldMetadataList` on object metadata.
- `SettingsObjectSearchSection` now reads
`objectMetadataItem.searchFieldMetadatas` instead of parsing
`asExpression`; new `SearchFieldMetadataItem` type, fragment, and
mapping updates.

### Upgrade commands (2.18)
-
`2-18-instance-command-fast-...-add-ts-vector-field-metadata-id-to-search-field-metadata`
-
`2-18-instance-command-fast-...-make-search-field-metadata-fks-deferrable`
-
`2-18-instance-command-slow-...-backfill-ts-vector-field-metadata-id-on-search-field-metadata`

(These were relocated from 2.16 to 2.18 and re-timestamped into an
ordered block - add column -> make FK deferrable -> backfill data -
since 2.16/2.17 are released.)

### Tests
- Updated search-vector side-effect integration specs to assert behavior
(search works) rather than the now-removed `asExpression`; removed the
obsolete expression-validation specs; refreshed the application-sync
snapshot (`universalSettings: null`).

## Upgrade / compatibility notes
- Existing workspaces keep their stored `settings` until a later
cleanup; nothing reads it anymore. The new derivation drives all DDL
going forward.
- Schema changes are gated behind the 2.18 instance commands above.

## Known follow-up (separate PR)
https://github.com/twentyhq/core-team-issues/issues/2620
- The column rebuild (`DROP`/`ADD` of the `searchVector` STORED column)
cascade-drops its GIN index and does not recreate it - a pre-existing
regression on `main` inherited here. A follow-up PR will fix the rebuild
handler to recreate the GIN index and add a 2.18 workspace command to
recompute every search vector + strip the deprecated settings.
(Planned.)

## Test plan
- [ ] `npx nx typecheck twenty-server` / `twenty-front`
- [ ] `npx nx lint:diff-with-main twenty-server` / `twenty-front`
- [ ] Server integration: create/update/delete field, rename indexed
field, update object - search returns expected records
- [ ] Run the 2.18 instance commands on a seeded DB; verify
`tsVectorFieldMetadataId` backfilled and FKs deferrable
- [ ] Frontend: object Search settings tab lists the correct searchable
fields (no `asExpression` parsing)

close https://github.com/twentyhq/core-team-issues/issues/2587

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packages/twenty-server/src/engine/dataloaders/dataloader.interface.ts

@@ -5,6 +5,7 @@ import {
   type FieldMetadataLoaderPayload,
   type IndexFieldMetadataLoaderPayload,
   type IndexMetadataLoaderPayload,
+  type SearchFieldMetadataLoaderPayload,
   type IsConfiguredLoaderPayload,
   type MorphRelationLoaderPayload,
   type StandardApplicationIdLoaderPayload,
@@ -23,6 +24,7 @@ import { type RelationDTO } from 'src/engine/metadata-modules/field-metadata/dto
 import { type IndexFieldMetadataDTO } from 'src/engine/metadata-modules/index-metadata/dtos/index-field-metadata.dto';
 import { type IndexMetadataDTO } from 'src/engine/metadata-modules/index-metadata/dtos/index-metadata.dto';
 import { type ObjectMetadataDTO } from 'src/engine/metadata-modules/object-metadata/dtos/object-metadata.dto';
+import { type SearchFieldMetadataDTO } from 'src/engine/metadata-modules/search-field-metadata/dtos/search-field-metadata.dto';
 import { type ViewFieldGroupDTO } from 'src/engine/metadata-modules/view-field-group/dtos/view-field-group.dto';
 import { type ViewFieldDTO } from 'src/engine/metadata-modules/view-field/dtos/view-field.dto';
 import { type ViewFilterGroupDTO } from 'src/engine/metadata-modules/view-filter-group/dtos/view-filter-group.dto';
@@ -53,6 +55,11 @@ export interface IDataloaders {
     IndexFieldMetadataDTO[]
   >;
 
+  searchFieldMetadataLoader: DataLoader<
+    SearchFieldMetadataLoaderPayload,
+    SearchFieldMetadataDTO[]
+  >;
+
   objectMetadataLoader: DataLoader<
     ObjectMetadataLoaderPayload,
     ObjectMetadataDTO | null

packages/twenty-server/src/engine/dataloaders/dataloader.service.ts

@@ -31,6 +31,7 @@ import { resolveMorphRelationsFromFlatFieldMetadata } from 'src/engine/metadata-
 import { resolveRelationFromFlatFieldMetadata } from 'src/engine/metadata-modules/flat-field-metadata/utils/resolve-relation-from-flat-field-metadata.util';
 import { fromFlatObjectMetadataToObjectMetadataDto } from 'src/engine/metadata-modules/flat-object-metadata/utils/from-flat-object-metadata-to-object-metadata-dto.util';
 import { getMorphNameFromMorphFieldMetadataName } from 'src/engine/metadata-modules/flat-object-metadata/utils/get-morph-name-from-morph-field-metadata-name.util';
+import { fromFlatSearchFieldMetadataToSearchFieldMetadataDto } from 'src/engine/metadata-modules/flat-search-field-metadata/utils/from-flat-search-field-metadata-to-search-field-metadata-dto.util';
 import { fromFlatViewFieldGroupToViewFieldGroupDto } from 'src/engine/metadata-modules/view-field-group/utils/from-flat-view-field-group-to-view-field-group-dto.util';
 import { fromFlatViewFieldToViewFieldDto } from 'src/engine/metadata-modules/view-field/utils/from-flat-view-field-to-view-field-dto.util';
 import { fromFlatViewFilterToViewFilterDto } from 'src/engine/metadata-modules/view-filter/utils/from-flat-view-filter-to-view-filter-dto.util';
@@ -41,6 +42,7 @@ import { type IndexFieldMetadataDTO } from 'src/engine/metadata-modules/index-me
 import { type IndexMetadataDTO } from 'src/engine/metadata-modules/index-metadata/dtos/index-metadata.dto';
 import { ObjectMetadataDTO } from 'src/engine/metadata-modules/object-metadata/dtos/object-metadata.dto';
 import { type ObjectMetadataEntity } from 'src/engine/metadata-modules/object-metadata/object-metadata.entity';
+import { type SearchFieldMetadataDTO } from 'src/engine/metadata-modules/search-field-metadata/dtos/search-field-metadata.dto';
 
 export type RelationMetadataLoaderPayload = {
   workspaceId: string;
@@ -76,6 +78,11 @@ export type IndexFieldMetadataLoaderPayload = {
   indexMetadata: Pick<IndexMetadataInterface, 'id'>;
 };
 
+export type SearchFieldMetadataLoaderPayload = {
+  workspaceId: string;
+  objectMetadata: Pick<ObjectMetadataEntity, 'id'>;
+};
+
 export type ObjectMetadataLoaderPayload = {
   workspaceId: string;
   objectMetadataId: string;
@@ -145,6 +152,7 @@ export class DataloaderService {
     const fieldMetadataLoader = this.createFieldMetadataLoader();
     const indexMetadataLoader = this.createIndexMetadataLoader();
     const indexFieldMetadataLoader = this.createIndexFieldMetadataLoader();
+    const searchFieldMetadataLoader = this.createSearchFieldMetadataLoader();
     const objectMetadataLoader = this.createObjectMetadataLoader();
     const viewFieldGroupsByViewIdLoader =
       this.createViewFieldGroupsByViewIdLoader();
@@ -168,6 +176,7 @@ export class DataloaderService {
       fieldMetadataLoader,
       indexMetadataLoader,
       indexFieldMetadataLoader,
+      searchFieldMetadataLoader,
       objectMetadataLoader,
       viewFieldGroupsByViewIdLoader,
       viewFieldsByViewFieldGroupIdLoader,
@@ -306,6 +315,46 @@ export class DataloaderService {
     );
   }
 
+  private createSearchFieldMetadataLoader() {
+    return new DataLoader<
+      SearchFieldMetadataLoaderPayload,
+      SearchFieldMetadataDTO[]
+    >(async (dataLoaderParams: SearchFieldMetadataLoaderPayload[]) => {
+      const workspaceId = dataLoaderParams[0].workspaceId;
+      const objectMetadataIds = dataLoaderParams.map(
+        (dataLoaderParam) => dataLoaderParam.objectMetadata.id,
+      );
+
+      const { flatSearchFieldMetadataMaps, flatObjectMetadataMaps } =
+        await this.flatEntityMapsCacheService.getOrRecomputeManyOrAllFlatEntityMaps(
+          {
+            workspaceId,
+            flatMapsKeys: [
+              'flatSearchFieldMetadataMaps',
+              'flatObjectMetadataMaps',
+            ],
+          },
+        );
+
+      return objectMetadataIds.map((objectMetadataId) => {
+        const flatObjectMetadata = findFlatEntityByIdInFlatEntityMapsOrThrow({
+          flatEntityId: objectMetadataId,
+          flatEntityMaps: flatObjectMetadataMaps,
+        });
+
+        const searchFieldMetadatas =
+          findManyFlatEntityByIdInFlatEntityMapsOrThrow({
+            flatEntityIds: flatObjectMetadata.searchFieldMetadataIds,
+            flatEntityMaps: flatSearchFieldMetadataMaps,
+          });
+
+        return searchFieldMetadatas.map(
+          fromFlatSearchFieldMetadataToSearchFieldMetadataDto,
+        );
+      });
+    });
+  }
+
   private createFieldMetadataLoader() {
     return new DataLoader<FieldMetadataLoaderPayload, FieldMetadataDTO[]>(
       async (dataLoaderParams: FieldMetadataLoaderPayload[]) => {