Webhook should deny clusters with common Ip addresses

[mcbenjemaa]

What steps did you take and what happened: [A clear and concise description of what the bug is.]

I created a cluster with a specific IP range and later created another cluster with another IP range that intersect with the other range, the cluster starts provisioning, and a new machine has the same IP as another machine from the other cluster, which leads to a conflict.

I got an apiserver error cannot verify certificate cause of the conflict.

What did you expect to happen:

The new cluster has to be rejected prior to provisioning.

Anything else you would like to add: [Miscellaneous information that will assist in solving the issue.]

Environment:

• Cluster-api-provider-proxmox version: v0.1.0
• Kubernetes version: (use kubectl version): v1.27.8
• OS (e.g. from /etc/os-release): ubuntu