I cannot update a join table with manyToMany property using nestjs and typeorm - nestjs

Question

I have set up a many to many relation between a user table and a spot table.
Here is the user entity:
#Entity('user')
export class UserEntity {
#PrimaryGeneratedColumn()
id: number;
#Column({ default: '' })
first_name: string;
#Column({ default: '' })
last_name: string;
#Column({ default: '' })
email: string;
#Column({ default: '' })
adress: string;
#Column({ type: 'timestamp', default: () => 'CURRENT_TIMESTAMP' })
createdAt: Date;
#ManyToMany(() => SpotEntity, (spot) => spot.users)
#JoinTable({
name: 'spot_user',
joinColumn: {
name: 'user_id',
referencedColumnName: 'id',
},
inverseJoinColumn: {
name: 'spot_id',
referencedColumnName: 'id',
},
})
spots: Spot[];
}
And here is the spot entity:
#Entity('spot')
export class SpotEntity {
#PrimaryGeneratedColumn()
id: number;
#Column({ default: '' })
title: string;
#Column({ default: '' })
description: string;
#Column({ default: '' })
address: string;
#Column({ default: '' })
coordinates: string;
#Column({ type: 'timestamp', default: () => 'CURRENT_TIMESTAMP' })
createdAt: Date;
#ManyToOne(() => TagEntity, (tag) => tag.spots)
tag: TagEntity;
#ManyToMany(() => UserEntity, (user) => user.spots)
users: User[];
}
This creates the join table as it should.
But now I am a bit confused as to how add a spot to a user.
To do so I added a service like so, which has access to both user and spot repository:
I a able to get the spot and the user, but the spot never saves into the user, and the join table is never updated.
async addSpotToUser(id?: number, spotId?: number): Promise<void> {
const mySpot = Object.values(spotId)[0];
const user = await this.userRepository.findOneBy({ id: Number(id) });
const spot = await this.spotRepository.findOneBy({ id: mySpot });
user.spots.push(spot);
this.userRepository.save(user);
}
}