Automated Firewall Update for Google Services

The goal is to update the firewall rule that allows all VMs to reach all google services but not those from google cloud customers.

According to [Google Suport]](https://support.google.com/a/answer/10026322?hl=en) there are two endpoints from google. One is providing information about all IP ranges announced by Google and one with all ranges used by google could customers.

While the second list of IP ranges is a subset of the first we need to create a diffset which can easily be done using the package netaddr.

The can be updated periodically using cloud scheduler and cloud functions.

For this to work:

1. a service account used by the cloud function requires 'Deployment Manager Editor' permission.
2. and the service account used by the scheduler requires permission to invoke the cloud function.

For HTTP:

{
    "project": "xxxx",
    "network": "xxxx",
    "firewall_rule_name": "allow-egress-google-services-automated",
    "firewall_rule_description": ""
}

For PubSub

{
    "data": "a base64 encoded string of the dict above"
}