limit open payments per user

payments/views.py

@@ -27,6 +27,10 @@ def new(request):
     if request.method != 'POST':
         return redirect('account:index')
 
+    if Payment.objects.filter(user=request.user, status='new').count() > 10:
+        messages.error(request, "Too many open payments.")
+        return redirect('account:index')
+
     form = NewPaymentForm(request.POST)
 
     if not form.is_valid():