Django lastseen

class LastseenProduct(models.Model):
    product = models.ForeignKey(Product, on_delete=models.CASCADE)
    created = models.DateTimeField(auto_now_add=True, verbose_name='Дата создания')
    updated = models.DateTimeField(auto_now=True, verbose_name='Дата изменения')

    def __str__(self):
        return f'Просмотренно (Товар : {self.product})'


class Lastseen(models.Model):
    user = models.ForeignKey(Customer, null=True, on_delete=models.CASCADE)
    lastseen_products = models.ManyToManyField(LastseenProduct, related_name='related_lastseen_products')
    for_anonymous_user = models.BooleanField(default=False)
    session_key = models.CharField(max_length=32, null=True)


    class Meta:
        constraints = [
            models.constraints.UniqueConstraint(fields=['lastseen_products'], name='unique_object')
        ]

    def __str__(self):
        return f'Пользователь: {self.user}, кол-во: {self.lastseen_products.count()} {self.lastseen_products.all()}'