[opennebula] turn VM into a product

opennebula/models.py

@@ -2,6 +2,7 @@ import uuid
 from django.db import models
 from django.contrib.auth import get_user_model
 from django.contrib.postgres.fields import JSONField
+from uncloud_pay.models import Product
 
 # ungleich specific
 storage_class_mapping = {
@@ -10,9 +11,8 @@ storage_class_mapping = {
     'hdd': 'hdd'
 }
 
-class VM(models.Model):
+class VM(Product):
     vmid = models.IntegerField(primary_key=True)
-    owner = models.ForeignKey(get_user_model(), on_delete=models.CASCADE)
     data = JSONField()
 
     @property