Files v2 - Add new FILES field type (#17236)

In this PR : 
- New field type FieldMetadataType.FILES added (as jsonb in DB)
- Backend: GraphQL types, validation, REST API schema, data processor
handling
- Frontend: field configuration in settings
- Feature flag IS_FILES_FIELD_ENABLED to gate the feature
- Integration tests for create/filter validation
- Dev seed: Feature flag enabled + FILES field on survey result object


To do in next PRs : 
- Backend : 
-- new workspaceFile controller (for download) & new workspaceFile
upload resolver (for upload)
-- pre-hook/post-hook to ensure fileId existence + listener to ensure
cleaning
- Frontend : FILES field display/edit in table view, record, ...

packages/twenty-server/src/engine/utils/convert-object-metadata-to-schema-properties.util.ts

@@ -1,7 +1,8 @@
 import {
   FieldMetadataType,
-  type FieldMetadataSettings,
+  FILE_CATEGORIES,
   NumberDataType,
+  type FieldMetadataSettings,
 } from 'twenty-shared/types';
 import { isDefined } from 'twenty-shared/utils';
 
@@ -330,6 +331,31 @@ export const convertObjectMetadataToSchemaProperties = ({
           },
         };
         break;
+      case FieldMetadataType.FILES:
+        itemProperty = {
+          type: 'array',
+          items: {
+            type: 'object',
+            properties: {
+              fileId: {
+                type: 'string',
+                format: 'uuid',
+              },
+              label: {
+                type: 'string',
+              },
+              ...(forResponse
+                ? {
+                    fileCategory: {
+                      type: 'string',
+                      enum: Object.values(FILE_CATEGORIES),
+                    },
+                  }
+                : {}),
+            },
+          },
+        };
+        break;
       default:
         itemProperty = getFieldProperties(field);
         break;