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.ts

@@ -0,0 +1,42 @@
+export const DEFAULT_RELATION_FIELDS = ['id', 'code', 'name'] as const;
+export const USER_RELATION_FIELDS = ['id', 'username'] as const;
+
+export type DefaultRelation = {
+  readonly id: string;
+  readonly code: string;
+  readonly name: string;
+};
+
+export type UserRelation = {
+  readonly id: string;
+  readonly username: string;
+};
+
+export function pickRelation<T, K extends keyof NonNullable<T>>(
+  source: T | null | undefined,
+  fields: readonly K[],
+): Pick<NonNullable<T>, K> | null {
+  if (source == null) {
+    return null;
+  }
+  const result = {} as Pick<NonNullable<T>, K>;
+  for (const field of fields) {
+    result[field] = source[field];
+  }
+  return result;
+}
+
+export function pickDefaultRelation(
+  source: DefaultRelation | null | undefined,
+): DefaultRelation | null {
+  return pickRelation(source, DEFAULT_RELATION_FIELDS);
+}
+
+export function pickUserRelation(source: UserRelation): UserRelation {
+  return (
+    pickRelation(source, USER_RELATION_FIELDS) ?? {
+      id: source.id,
+      username: source.username,
+    }
+  );
+}