Allow adding trust anchors

[siegfriedweber]

Users should be able to add trust anchors. This is required, if e.g. OpenSearch should connect to a self-hosted S3 instance which is signed by a corporate certificate authority, see e.g. #56.

The CRD could be extended as follows:

---
apiVersion: opensearch.stackable.tech/v1alpha1
kind: OpenSearchCluster
spec:
  nodes:
    config:
      extraTrustAnchors:
        - value: <string>
        - valueFrom:
            configMapKeyRef:
              name: <string>
              key: <string>
        - valueFrom:
            secretKeyRef:
              name: <string>
              key: <string>

Workaround

It is already possible to add trust anchors via podOverrides:

---
apiVersion: opensearch.stackable.tech/v1alpha1
kind: OpenSearchCluster
spec:
  nodes:
    podOverrides:
      spec:
        initContainers:
          - name: init-system-keystore
            image: oci.stackable.tech/sdp/opensearch:3.1.0-stackable0.0.0-dev
            command:
              - update-ca-trust
            args:
              - extract
              - --output
              - /stackable/ca-trust
            volumeMounts:
              - name: system-trust-store
                mountPath: /stackable/ca-trust
                readOnly: false
              - name: custom-trust-anchors
                mountPath: /etc/pki/ca-trust/source/anchors/custom-tls.crt
                subPath: tls.crt
                readOnly: true
        containers:
          - name: opensearch
            volumeMounts:
              - name: system-trust-store
                mountPath: /etc/pki/java/cacerts
                subPath: java/cacerts
                readOnly: true
        volumes:
          - name: custom-trust-anchors
            secret:
              secretName: secret-with-trust-anchors
              defaultMode: 0o660
          - name: system-trust-store
            emptyDir:
              sizeLimit: 10Mi