add a new field to KBItem model to keep track of all users who voted, and make changes to the vote function so that it checks whether a user has already votred

helpdesk/models.py

@@ -988,6 +988,7 @@ class KBItem(models.Model):
     An item within the knowledgebase. Very straightforward question/answer
     style system.
     """
+    voted_by= models.ManyToManyField(settings.AUTH_USER_MODEL)
     category = models.ForeignKey(
         KBCategory,
         on_delete=models.CASCADE,