Support rDNS (ptr) records for instances

[jappeace]

Hi, I require this in gce https://cloud.google.com/compute/docs/instances/create-ptr-record
which is in api like this:

     "networkInterfaces":
     [
      {
       "network": "[NETWORK]",
       "accessConfigs":
     [
      {
       "publicPtrDomainName": "[DOMAIN_NAME]",
       "setPublicPtr": true,
       "type": "ONE_TO_ONE_NAT",
       "name": "External IP"
      }
     ]
    }
   ]

Which is almost implemented here:

nixops/nixops/backends/gce.py

Line 554 in 6da4190

"/zones/{0}/instances/{1}/addAccessConfig?networkInterface=nic0"

How do I express that in nix, and then make it work together with python? I'd be happy to implement this myself but I have trouble getting my head around how to bridge the gap between the two.