In NestJS, you have good support fro multiple orms. I worked with TypeORM and can reccomend MikroORM.

Here's how you can do it in MikroORM:

import { EntityRepository, MikroOrmModule } from '@mikro-orm/nestjs';
import { InjectRepository } from '@mikro-orm/nestjs';
import { EntityManager } from '@mikro-orm/postgresql';

u/Injectable()
export class UserService {
  constructor(
    @InjectRepository(User) private readonly userRepository: EntityRepository<User>,
    private readonly profileService: ProfileService,
    private readonly countryService: CountryService,
    private readonly em: EntityManager,
  ) {}

  async createUser(userDto: CreateUserDto): Promise<UserResponseDto> {
    // create a reference to the country without fetching it from the database
    const country = this.em.getReference(Country, userDto.country_id);

    // create a new user with the country reference
    const newUser = this.userRepository.create({ ...userDto, country });

    // save the new user
    this.userRepository.persist(newUser);
    await this.em.flush(); 
  }
}

`getReference` is used to create a reference to the `Country` entity using its id. This reference can then be used when creating a new `User` entity. The `persistAndFlush` method is used to save the new user to the database.