Wrap VM creation in database transaction

uncloud/uncloud_vm/views.py

@@ -1,3 +1,4 @@
+from django.db import transaction
 from django.shortcuts import render
 
 from django.contrib.auth.models import User
@@ -27,10 +28,10 @@ class VMProductViewSet(ProductViewSet):
     def get_queryset(self):
         return VMProduct.objects.filter(owner=self.request.user)
 
+    # Use a database transaction so that we do not get half-created structure
+    # if something goes wrong.
+    @transaction.atomic
     def create(self, request):
-        # TODO: what if something blows-up midway?
-        # => need a transaction
-
         # Create base order.
         order = Order.objects.create(
                 recurring_period=RecurringPeriod.PER_MONTH,