[vpn] begin to introduce save() method

The save() and delete() method will create/manage the orders

uncloud_django_based/uncloud/uncloud_net/models.py

@@ -173,11 +173,11 @@ class VPNNetwork(Product):
 
     wireguard_public_key = models.CharField(max_length=48)
 
+    def save(self, *args, **kwargs):
+        super().save(*args, **kwargs)
+
     def delete(self, *args, **kwargs):
         self.network.status = 'free'
         self.network.save()
         super().save(*args, **kwargs)
         print("deleted {}".format(self))
-
-# managing deletion
-# - record free network (?)