Querying many to one on mongoose - mongodb

Question

Supposed I have two model User and Car, and they have one to many, many to one relationship
User Model
#modelOptions({ schemaOptions: { collection: 'users' } })
export class User extends TimeStamps {
#prop({ required: true })
name!: string
#prop({ required: true })
age!: number
#prop({ ref: () => Car })
cars?: Ref<Car>[]
}
Car Model
#modelOptions({ schemaOptions: { collection: 'cars' } })
export class Car extends TimeStamps {
#prop({ required: true })
model!: string
#prop({ required: true })
plateNumber!: string
#prop({ required: true })
type!: string
#prop({ ref: () => User })
user?: Ref<User>
}
I can save many cars into user using
async attachCarsToUser(userId: string, carsId: string[]) {
return this.findOneAndUpdate(
{ _id: userId },
{
$addToSet: {
cars: {
$each: carsId
}
}
}
)
}
and i can get the result by using:
async getAllUsers() {
return await this.usersRepository.find().populate('cars').lean()
}
Now, I can get the result correctly as it saved many cars on the user.
My question is how can I get like a bidirectional relationship on these two models such that when I query using these code:
async getAllCars() {
return await this.carsRepository.find().populate('user').lean()
}
I want to get the specific user on a car, however it doesn't work that way. and it produce result like this even if theres a field for user and also I already used the populate()
Im fairly new to monggodb, any idea what's the approach to this? Do i need to save the id of user on a car too?
BTW I used typegoose and under the hood it uses mongoose.