Writing Services with `Effect.gen`

const UserService = Layer.sync(UserServiceTag, () => ({
     findOne(filter: Partial<UserEntity>) {
        return Effect.gen(function* {
          const db = yield* DbServiceTag
          const userRepo = db.getRepository(UserEntity)
          return Effect.promise(() => userRepo.findOne({where: filter}))
        })
     }
})