Make additional validation for CM of cozystack

[gecube]

Hi!

Right now it is easy to make a typo when preparing the cozy-stack configmap:

apiVersion: v1
kind: ConfigMap
metadata:
  name: cozystack
  namespace: cozy-system
data:
  bundle-name: "paas-full"
  ipv4-pod-cidr: "100.64.0.0/16"
  ipv4-pod-gateway: "10.64.0.1"
  ipv4-svc-cidr: "10.65.0.0/16"
  ipv4-join-cidr: "100.66.0.0/16"

I think it could be beneficial to install before applying some kind of webhook which will check the parameters and write meaningful errors (like "bundle name is not supported") or even switch from CM to our own CRD with a proper schema.

[mrkhachaturov]

@gecube

I am working on operator for cozystack.