Making optional spec.networkProfile.domain and renaming it to certSANs

[prometherion]

Discussed in #48

^{Originally posted by prometherion May 31, 2022}

We know that Kamaji could be exposed in several ways, from dynamic Load Balancer to bare IP or Ingress resources.

In the latter case, we already support the required hostname to perform host matching, as well as generate the certificate required for it.

However, in some circumstances, we could have a LoadBalancer reachable through a DNS, and suddenly, by a hostname that is not reported in any Kubernetes primitive.

With that said, we could add the new array of strings named certSANs with the following default values:

1. localhost
2. 127.0.0.1
3. 0.0.0.0

With such an option, an operator can easily add an arbitrary hostname, without worrying about the IP address or Ingress hostname used to expose the Tenant Control Plane since it's already covered by Kamaji.