Enhance branch management with foreign key relation handling

- Updated `BranchesModule` to include foreign key relations in list and write responses, ensuring they are represented as nested objects using `pickRelation`.
- Introduced new `relation-response.mdc` file to define guidelines for embedding foreign key relations.
- Modified `BranchesRepository` to support fetching related `division`, `createdByUser`, and `updatedByUser` data.
- Updated DTOs and service methods to reflect changes in response structure, removing direct foreign key IDs.
- Added unit tests to validate the new relation handling in branches service and repository.
- Enhanced e2e tests to verify the correct structure of branch responses with nested relations.

src/common/http/response/relation-fields.spec.ts

@@ -0,0 +1,78 @@
+import {
+  DEFAULT_RELATION_FIELDS,
+  pickDefaultRelation,
+  pickRelation,
+  pickUserRelation,
+  USER_RELATION_FIELDS,
+} from './relation-fields';
+
+describe('pickRelation', () => {
+  const catalog = {
+    id: 'div-1',
+    code: 'JKT',
+    name: 'Jakarta',
+    status: 'active',
+    extra: 'secret',
+  };
+
+  const user = {
+    id: 'user-1',
+    username: 'admin',
+    passwordHash: 'hashed',
+  };
+
+  it('picks default id, code, name fields', () => {
+    expect(pickRelation(catalog, DEFAULT_RELATION_FIELDS)).toEqual({
+      id: 'div-1',
+      code: 'JKT',
+      name: 'Jakarta',
+    });
+  });
+
+  it('picks a custom field list for users', () => {
+    expect(pickRelation(user, USER_RELATION_FIELDS)).toEqual({
+      id: 'user-1',
+      username: 'admin',
+    });
+  });
+
+  it('returns null for null or undefined sources', () => {
+    const missing: typeof catalog | null = null;
+    const unset: typeof catalog | undefined = undefined;
+    expect(
+      pickRelation<typeof catalog, (typeof DEFAULT_RELATION_FIELDS)[number]>(
+        missing,
+        DEFAULT_RELATION_FIELDS,
+      ),
+    ).toBeNull();
+    expect(
+      pickRelation<typeof catalog, (typeof DEFAULT_RELATION_FIELDS)[number]>(
+        unset,
+        DEFAULT_RELATION_FIELDS,
+      ),
+    ).toBeNull();
+  });
+
+  it('does not copy fields outside the list', () => {
+    const picked = pickRelation(catalog, DEFAULT_RELATION_FIELDS);
+    expect(picked).not.toHaveProperty('status');
+    expect(picked).not.toHaveProperty('extra');
+  });
+});
+
+describe('pickDefaultRelation / pickUserRelation', () => {
+  it('maps catalog and user sources without leaking extra fields', () => {
+    expect(
+      pickDefaultRelation({
+        id: 'div-1',
+        code: 'JKT',
+        name: 'Jakarta',
+      }),
+    ).toEqual({ id: 'div-1', code: 'JKT', name: 'Jakarta' });
+    expect(pickDefaultRelation(null)).toBeNull();
+    expect(pickUserRelation({ id: 'user-1', username: 'admin' })).toEqual({
+      id: 'user-1',
+      username: 'admin',
+    });
+  });
+});