Allow to Specify ENV Vars in the Scan CRD

[J12934]

Closes #48

Needs to be documented, see #47

Can be used like this:

kubectl create secret generic example-secret --from-literal=target=example.com

apiVersion: "execution.experimental.securecodebox.io/v1"
kind: Scan
metadata:
  name: "nmap-from-secret"
spec:
  scanType: "nmap"
  env:
    - name: TARGET
      valueFrom:
        secretKeyRef:
          name: example-secret
          key: target
  parameters:
    - "-p22,443"
    - "$(TARGET)"

[rfelber]

Nice 🤙