JugarAlPadel/parejas-models.py

from django.conf import settings

class Reserva(models.Model):
    evento = models.ForeignKey(Evento, on_delete=models.CASCADE, related_name='reservas')
    usuario = models.ForeignKey(settings.AUTH_USER_MODEL, on_delete=models.CASCADE, related_name='reservas')
    acompanante = models.ForeignKey(
        settings.AUTH_USER_MODEL,
        on_delete=models.SET_NULL,
        null=True,
        blank=True,
        related_name='reservas_como_acompanante'
    )
    fecha_reserva = models.DateTimeField(auto_now_add=True)

    class Meta:
        unique_together = ('evento', 'usuario')

    def __str__(self):
        if self.acompanante:
            return f"{self.usuario} y {self.acompanante} en {self.evento}"
        return f"{self.usuario} en {self.evento}"