Refactor new relation sync (#11711)

In this PR:
- this should fix the sync metadata for new relation system

This goes with the recent PR:
https://github.com/twentyhq/twenty/pull/11725

What we want:
- ONE_TO_MANY relations should have no joinColumn and no onDelete
- MANY_TO_ONE should have both

packages/twenty-server/src/engine/metadata-modules/field-metadata/field-metadata.service.ts

@@ -355,7 +355,7 @@ export class FieldMetadataService extends TypeOrmQueryService<FieldMetadataEntit
       });
 
       if (fieldMetadata.type === FieldMetadataType.RELATION) {
-        const isManyToManyRelation =
+        const isManyToOneRelation =
           (fieldMetadata as FieldMetadataEntity<FieldMetadataType.RELATION>)
             .settings?.relationType === RelationType.MANY_TO_ONE;
 
@@ -385,7 +385,7 @@ export class FieldMetadataService extends TypeOrmQueryService<FieldMetadataEntit
                 columns: [
                   {
                     action: WorkspaceMigrationColumnActionType.DROP,
-                    columnName: isManyToManyRelation
+                    columnName: isManyToOneRelation
                       ? `${(fieldMetadata as FieldMetadataEntity<FieldMetadataType.RELATION>).settings?.joinColumnName}`
                       : `${(targetFieldMetadata as FieldMetadataEntity<FieldMetadataType.RELATION>).settings?.joinColumnName}`,
                   } satisfies WorkspaceMigrationColumnDrop,

packages/twenty-server/src/engine/metadata-modules/object-metadata/services/object-metadata-field-relation.service.ts

@@ -100,7 +100,6 @@ export class ObjectMetadataFieldRelationService {
         ...sourceFieldMetadata,
         settings: {
           relationType: RelationType.ONE_TO_MANY,
-          onDelete: RelationOnDeleteAction.CASCADE,
         },
         relationTargetObjectMetadataId: targetObjectMetadata.id,
         relationTargetFieldMetadataId: targetFieldMetadata.id,

packages/twenty-server/src/engine/metadata-modules/workspace-migration/factories/relation-column-action.factory.ts

@@ -55,6 +55,12 @@ export class RelationColumnActionFactory extends ColumnActionAbstractFactory<Fie
       return [];
     }
 
+    if (
+      currentFieldMetadata.settings.relationType === RelationType.ONE_TO_MANY
+    ) {
+      return [];
+    }
+
     const currentJoinColumnName = currentFieldMetadata.settings.joinColumnName;
     const alteredJoinColumnName = alteredFieldMetadata.settings.joinColumnName;