Add API documentation for TrackGo HTTP API and enhance employee management features

- Created a new `api.md` file detailing the TrackGo HTTP API, including authentication, user management, and employee operations.
- Updated `Employee` type to simplify user relation handling by replacing `UserRelation` with a more concise structure.
- Enhanced filtering capabilities in employee queries to support an array of positions.
- Refactored employee-related services and repositories to accommodate the new position filtering logic.
- Added unit and e2e tests to validate the new API documentation and employee management functionalities.

test/employees.e2e-spec.ts

@@ -202,6 +202,60 @@ describe('Employees (e2e)', () => {
       .expect(204);
   });
 
+  it('lists employees filtered by an array of positions', async () => {
+    const suffix = Date.now().toString().slice(-6);
+    const auth = { Authorization: `Bearer ${adminAccessToken}` };
+    const base = {
+      name: 'Ada Lovelace',
+      phone: '+6281234567890',
+    };
+
+    const sales = await request(app.getHttpServer())
+      .post('/employees')
+      .set(auth)
+      .send({ ...base, code: `PS_${suffix}`, position: 'sales' })
+      .expect(201);
+    const driver = await request(app.getHttpServer())
+      .post('/employees')
+      .set(auth)
+      .send({ ...base, code: `PD_${suffix}`, position: 'driver' })
+      .expect(201);
+    const crew = await request(app.getHttpServer())
+      .post('/employees')
+      .set(auth)
+      .send({ ...base, code: `PC_${suffix}`, position: 'crew' })
+      .expect(201);
+
+    const salesId = (sales.body as { id: string }).id;
+    const driverId = (driver.body as { id: string }).id;
+    const crewId = (crew.body as { id: string }).id;
+
+    const single = await request(app.getHttpServer())
+      .get(`/employees?position=sales&code=${suffix}`)
+      .set(auth)
+      .expect(200);
+    const singleIds = (single.body as { data: { id: string }[] }).data.map(
+      (row) => row.id,
+    );
+    expect(singleIds).toEqual([salesId]);
+
+    const multi = await request(app.getHttpServer())
+      .get(`/employees?position=sales&position=driver&code=${suffix}`)
+      .set(auth)
+      .expect(200);
+    const multiIds = (multi.body as { data: { id: string }[] }).data.map(
+      (row) => row.id,
+    );
+    expect(multiIds).toEqual(expect.arrayContaining([salesId, driverId]));
+    expect(multiIds).toHaveLength(2);
+    expect(multiIds).not.toContain(crewId);
+
+    await request(app.getHttpServer())
+      .get('/employees?position=pilot')
+      .set(auth)
+      .expect(400);
+  });
+
   it('imports employees from CSV', async () => {
     const suffix = Date.now().toString().slice(-6);
     const csv =