Fix consistency issuesin relation onDelete behavior while creating a new relation (#4372)

* Fix consistency issuesin relation onDelete behavior while creating a new relation

* Fix according to review

packages/twenty-server/src/metadata/object-metadata/object-metadata.service.ts

@@ -397,6 +397,7 @@ export class ObjectMetadataService extends TypeOrmQueryService<ObjectMetadataEnt
                 createdObjectMetadata,
               ),
               referencedTableColumnName: 'id',
+              onDelete: RelationOnDeleteAction.CASCADE,
             },
           ],
         },

packages/twenty-server/src/metadata/relation-metadata/relation-metadata.service.ts

@@ -26,6 +26,7 @@ import { generateMigrationName } from 'src/metadata/workspace-migration/utils/ge
 import {
   RelationMetadataEntity,
   RelationMetadataType,
+  RelationOnDeleteAction,
 } from './relation-metadata.entity';
 
 @Injectable()
@@ -209,6 +210,7 @@ export class RelationMetadataService extends TypeOrmQueryService<RelationMetadat
               isUnique:
                 relationMetadataInput.relationType ===
                 RelationMetadataType.ONE_TO_ONE,
+              onDelete: RelationOnDeleteAction.SET_NULL,
             },
           ],
         },

packages/twenty-server/src/workspace/workspace-migration-runner/utils/convert-on-delete-action-to-on-delete.util.ts

@@ -4,7 +4,7 @@ export const convertOnDeleteActionToOnDelete = (
   onDeleteAction: RelationOnDeleteAction | undefined,
 ): 'CASCADE' | 'SET NULL' | 'RESTRICT' | 'NO ACTION' | undefined => {
   if (!onDeleteAction) {
-    return;
+    return 'SET NULL';
   }
 
   switch (onDeleteAction) {