NestJS Modules, Guards, DTOs and DI Fixes

NESTJS USER CREATION ENDPOINT (complete module)

FILE: src/users/create-user.dto.ts
export class CreateUserDto {
  @IsEmail()
  email: string;
  @IsString() @MinLength(8) @MaxLength(64)
  password: string;
  @IsString() @MinLength(2) @MaxLength(50)
  firstName: string;
}

FILE: src/users/users.service.ts
@Injectable()
export class UsersService {
  constructor(private prisma: PrismaService, private hash: HashService) {}
  
  async createUser(dto: CreateUserDto) {
    const existing = await this.prisma.user.findUnique({where: {email: dto.email}});
    if (existing) throw new ConflictException("Email already registered");
    
    const hashed = await this.hash.bcrypt(dto.password);
    return this.prisma.user.create({
      data: {email: dto.email, hashedPassword: hashed, firstName: dto.firstName},
      select: {id: true, email: true, firstName: true, createdAt: true}
    });
  }
}

FILE: src/users/users.controller.ts
@Controller("users")
export class UsersController {
  constructor(private users: UsersService) {}
  
  @Post()
  @HttpCode(201)
  async register(@Body(new ValidationPipe()) dto: CreateUserDto) {
    return this.users.createUser(dto);
  }
}

FILE: src/users/users.module.ts
@Module({
  imports: [PrismaModule],
  controllers: [UsersController],
  providers: [UsersService, HashService]
})
export class UsersModule {}

RESULT: POST /users with CreateUserDto triggers validation, hashes password, checks uniqueness, persists to database, returns sanitized user object (no password hash). Errors: 400 for validation, 409 for duplicate email, 500 for database failure.