One membership for each user for each club

I’m creating models to manage clients and sports centers. Each customer can be enrolled in several centers only once of course. how should i proceed for this?

class Membership(models.Model):
    user = models.ForeignKey(User, on_delete=models.CASCADE, related_name='memberships')
    club = models.ForeignKey(Club, on_delete=models.CASCADE, related_name='memberships')
    points = models.PositiveIntegerField(default=0, blank=True, null=True)
    sub_date = models.DateField(auto_now_add=True)

    #other...

If I proceed in this way it is possible to create multiple subscriptions of the user to the same club. How can I solve the problem?

>Solution :

Use unique_together in the model Meta so that a Membership object cannot have the same user and club as another object:

class Membership(models.Model):
    ...
    class Meta:
        unique_together = ['user', 'club']

This will return an error if you use a form or the Django admin to create a membership that already exists with that user/club.