session updates. mostly

backend/playlist/models/vote.py

@@ -5,7 +5,7 @@ from .session import Session
 
 class Vote(models.Model):
     class Meta:
-        unique_together = ["user", "track"]
+        unique_together = ["user", "track", "session"]
     track = models.ForeignKey('Track', on_delete=models.CASCADE)
     user = models.ForeignKey(User, on_delete=models.CASCADE)
     points = models.IntegerField(validators=[MinValueValidator(1), MaxValueValidator(5)])