fix IndexFieldMetadata availability in IndexMetadata/ObjectMetadata in front (#12886)

Context : 
- IndexFieldMetadata was no longer available on 'objects' gql query
([since this PR](https://github.com/twentyhq/twenty/pull/12785)). Then,
unicity checks on import do not work anymore.

Fix : 
- Add a dataloader logic in indexFieldMetadata
- Add extra check in unicity hook on import

packages/twenty-front/src/modules/object-metadata/graphql/queries.ts

@@ -33,6 +33,13 @@ export const FIND_MANY_OBJECT_METADATA_ITEMS = gql`
             indexWhereClause
             indexType
             isUnique
+            indexFieldMetadataList {
+              id
+              fieldMetadataId
+              createdAt
+              updatedAt
+              order
+            }
           }
           fieldsList {
             id

packages/twenty-front/src/modules/object-metadata/types/IndexMetadataItem.ts

@@ -3,7 +3,10 @@ import { Index as GeneratedIndex } from '~/generated-metadata/graphql';
 
 export type IndexMetadataItem = Omit<
   GeneratedIndex,
-  '__typename' | 'indexFieldMetadatas' | 'objectMetadata'
+  | '__typename'
+  | 'indexFieldMetadatas'
+  | 'objectMetadata'
+  | 'indexFieldMetadataList'
 > & {
   __typename?: string;
   indexFieldMetadatas: IndexFieldMetadataItem[];

packages/twenty-front/src/modules/object-metadata/utils/mapPaginatedObjectMetadataItemsToObjectMetadataItems.ts

@@ -1,3 +1,4 @@
+import { IndexFieldMetadataItem } from '@/object-metadata/types/IndexFieldMetadataItem';
 import { IndexMetadataItem } from '@/object-metadata/types/IndexMetadataItem';
 import { objectMetadataItemSchema } from '@/object-metadata/validation-schemas/objectMetadataItemSchema';
 import { ObjectMetadataItemsQuery } from '~/generated-metadata/graphql';
@@ -26,7 +27,12 @@ export const mapPaginatedObjectMetadataItemsToObjectMetadataItems = ({
           (index) =>
             ({
               ...index,
-              indexFieldMetadatas: [],
+              indexFieldMetadatas: index.indexFieldMetadataList.map(
+                (indexFieldMetadata) =>
+                  ({
+                    ...indexFieldMetadata,
+                  }) satisfies IndexFieldMetadataItem,
+              ),
             }) satisfies IndexMetadataItem,
         ),
       } satisfies ObjectMetadataItem;