Draft: proof of concept for firewall machine deployments

[vknabel]

Description

Caution

DO NOT MERGE!

Proof of concept whether it is possible to use MachineDeployments to create and roll firewalls.
At a first glance this looks promising and it should be possible to implement.

To make this production ready:

• Add MetalStackFirewall which implements the infra machine protocol
  • with firewall rules
• Separate controller for the metalstackfirewall
  • needs to set machine.bootstrap.dataSecretName and needs to generate the secret containing User Data (this is slightly off the contract)

This should enable automatic rolling updates of the firewall whenever the firewall rules change. All handled by cluster api.

[vknabel]

This approach was worth a try, but we should not continue the efforts in this direction. Machines are defined as k8s nodes and are therefore required to be represented in the target cluster and get referenced from the machine resource.