Create self-signed certs for webhooks

[PK85]

Description

We'd like to keep btp-operator chart one to one with upstream. That means we need to handle self signed certificate creation in the controller codebase.

Right now to make btp-manager working we have that: https://github.com/kyma-incubator/sap-btp-service-operator/blob/main/chart/templates/webhook.yml

Golang cert logic, otters: https://github.com/kyma-project/warden/tree/main/internal/webhook Solution from huskies: https://github.com/kyma-project/kyma/tree/main/components/webhook-cert-init

AC

• [ ] 1) Implement logic for cert generation
• [ ] 2) Use it to create secret when BtpOperator resource is created. Then apply secret too.

  kind: Secret
  metadata:
  name: webhook-server-cert
  namespace: {{.Release.Namespace}}
  type: kubernetes.io/tls
  data:
  tls.crt: "{{ .Values.manager.certificates.selfSigned.crt }}"
  tls.key: "{{ .Values.manager.certificates.selfSigned.key }}"
  ---

• [ ] 3) document that flow. Decribe that we do not use functionality from chart, but we have our own solution.

[ukff]

PR: https://github.com/kyma-project/btp-manager/pull/209/files