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.

src/modules/configuration/employees/dto/employee.dto.spec.ts

@@ -0,0 +1,34 @@
+import { plainToInstance } from 'class-transformer';
+import { validate } from 'class-validator';
+import { ListEmployeesQueryDto } from './employee.dto';
+
+describe('ListEmployeesQueryDto', () => {
+  it('coerces a single position query value into an array', async () => {
+    const dto = plainToInstance(ListEmployeesQueryDto, { position: 'sales' });
+    expect(dto.position).toEqual(['sales']);
+    expect(await validate(dto)).toHaveLength(0);
+  });
+
+  it('accepts multiple positions', async () => {
+    const dto = plainToInstance(ListEmployeesQueryDto, {
+      position: ['sales', 'driver'],
+    });
+    expect(dto.position).toEqual(['sales', 'driver']);
+    expect(await validate(dto)).toHaveLength(0);
+  });
+
+  it('rejects an invalid position in the array', async () => {
+    const dto = plainToInstance(ListEmployeesQueryDto, {
+      position: ['pilot'],
+    });
+    expect(await validate(dto)).not.toHaveLength(0);
+  });
+
+  it('drops empty entries and deduplicates positions', async () => {
+    const dto = plainToInstance(ListEmployeesQueryDto, {
+      position: ['sales', '', 'sales'],
+    });
+    expect(dto.position).toEqual(['sales']);
+    expect(await validate(dto)).toHaveLength(0);
+  });
+});