fix: check payment status on instance level, used to be user level

billing/views.py

@@ -68,7 +68,7 @@ def generate_invoice(request, instance_name: str):
     delta = now - timedelta(seconds=(60 * 60 * 24 * 30))  # one month
 
     payment = None
-    for p in Payment.objects.filter(date__gt=(delta)):
+    for p in Payment.objects.filter(date__gt=(delta), instance_name=instance_name):
         if p.status == PaymentStatus.CONFIRMED:
             return HttpResponse("BAD REQUEST: Already paid", status=400)
         elif any([p.status == PaymentStatus.INPUT, p.status == PaymentStatus.WAITING]):