Implement controller to assign IP manually for pod

[mraerino]

This can be useful when other means of routing the traffic to a pod than a load balancer are used.

E.g. you could be using the ipvlan CNI plugin with Multus.

Example setup

apiVersion: apps/v1
kind: DaemonSet
metadata:
  name: coturn
  namespace: turn
spec:
  selector:
    matchLabels:
      app: turn
  template:
    metadata:
      labels:
        app: turn
        hcloud-ip-floater.cstl.dev/floating-ip: "78.47.226.156"
      annotations:
        k8s.v1.cni.cncf.io/networks: |
          [
            {
              "name": "relay-net",
              "ips": ["78.47.226.156/32"]
            }
          ]
    spec:
      # ...

---
apiVersion: k8s.cni.cncf.io/v1
kind: NetworkAttachmentDefinition
metadata:
  name: relay-net
  namespace: turn
spec:
  config: |
    {
      "cniVersion": "0.3.1",
      "type": "ipvlan",
      "master": "eth0",
      "mode": "l2",
      "ipam": {
        "type": "static"
      }
    }