Introducing view field group syncable entity (#17867)

## Context
Introduces a new viewFieldGroup entity that allows grouping view fields
into sections (e.g. "General", "Additional", "Other") within a view.

The page layout fields widget needs a way to organize fields into
sections. Today, views have no concept of field grouping. This PR
introduces the viewFieldGroup entity which sits between a view and its
viewFields, enabling section-based organization.

<img width="401" height="724" alt="Layout - V2 (customize visibility)"
src="https://github.com/user-attachments/assets/6376e2ab-44db-42bf-9d2c-758f56f6b548"
/>

---------

Co-authored-by: Charles Bochet <charles@twenty.com>

packages/twenty-server/src/engine/workspace-manager/workspace-migration/universal-flat-entity/constants/all-jsonb-properties-with-serialized-relation-by-metadata-name.constant.ts

@@ -15,6 +15,7 @@ export const ALL_JSONB_PROPERTIES_WITH_SERIALIZED_RELATION_BY_METADATA_NAME = {
   view: {},
   viewField: {},
   viewGroup: {},
+  viewFieldGroup: {},
   viewFilter: {},
   viewFilterGroup: {},
   index: {},

packages/twenty-server/src/engine/workspace-manager/workspace-migration/universal-flat-entity/constants/all-universal-metadata-relations.constant.ts

@@ -202,6 +202,7 @@ export const ALL_UNIVERSAL_METADATA_RELATIONS = {
       viewFilters: { metadataName: 'viewFilter' },
       viewFilterGroups: { metadataName: 'viewFilterGroup' },
       viewGroups: { metadataName: 'viewGroup' },
+      viewFieldGroups: { metadataName: 'viewFieldGroup' },
       // TODO migrate viewSort to v2
       viewSorts: null,
     },
@@ -224,11 +225,36 @@ export const ALL_UNIVERSAL_METADATA_RELATIONS = {
         universalForeignKey: 'viewUniversalIdentifier',
         isNullable: false,
       },
+      viewFieldGroup: {
+        metadataName: 'viewFieldGroup',
+        foreignKey: 'viewFieldGroupId',
+        universalFlatEntityForeignKeyAggregator:
+          'viewFieldUniversalIdentifiers',
+        universalForeignKey: 'viewFieldGroupUniversalIdentifier',
+        isNullable: true,
+      },
       workspace: null,
       application: null,
     },
     oneToMany: {},
   },
+  viewFieldGroup: {
+    manyToOne: {
+      view: {
+        metadataName: 'view',
+        foreignKey: 'viewId',
+        universalFlatEntityForeignKeyAggregator:
+          'viewFieldGroupUniversalIdentifiers',
+        universalForeignKey: 'viewUniversalIdentifier',
+        isNullable: false,
+      },
+      workspace: null,
+      application: null,
+    },
+    oneToMany: {
+      viewFields: { metadataName: 'viewField' },
+    },
+  },
   viewFilter: {
     manyToOne: {
       fieldMetadata: {

packages/twenty-server/src/engine/workspace-manager/workspace-migration/universal-flat-entity/types/universal-flat-view-field-group.type.ts

@@ -0,0 +1,7 @@
+import { type ViewFieldGroupEntity } from 'src/engine/metadata-modules/view-field-group/entities/view-field-group.entity';
+import { type UniversalFlatEntityFrom } from 'src/engine/workspace-manager/workspace-migration/universal-flat-entity/types/universal-flat-entity-from.type';
+
+export type UniversalFlatViewFieldGroup = UniversalFlatEntityFrom<
+  ViewFieldGroupEntity,
+  'viewFieldGroup'
+>;