Allow setting automountServiceAccountToken

[Aransh]

Purpose of this PR

By default, kubernetes enables "automountServiceAccountToken" for all pods.
This poses a security risk, as pods might get kube-api permissions unintentionally.
More specifically, this fails security compliance tests:
https://learn.microsoft.com/en-us/azure/governance/policy/samples/built-in-policies
https://www.azadvertizer.net/azpolicyadvertizer/kubernetes_block-automount-token.html

Solution - Disable "automountServiceAccountToken", create projected volume for the token, and mount it on relevant containers

Fixes #1189

Proposed changes:

• Allow setting this field for all spark-operator workloads and serviceAccounts
• No further changes needed, as projected volume can already be added using exiting "volumes" and "volumeMounts" values

Change Category

• Bugfix (non-breaking change which fixes an issue)
• Feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that could affect existing functionality)
• Documentation update

Rationale

Checklist

• I have conducted a self-review of my own code.
• I have updated documentation accordingly.
• I have added tests that prove my changes are effective or that my feature works.
• Existing unit tests pass locally with my changes.

Additional Notes

While default behavior remains unchanged, and anyone disabling "automountServiceAccountToken" should know the consequences (as this is a standard k8s feature, not a spark-operator one), I am adding an example values file for deploying the operator with it disabled:

controller:
  serviceAccount:
    automountServiceAccountToken: false
  volumes:
    - name: kube-api-access
      projected:
        defaultMode: 420
        sources:
        - serviceAccountToken:
            expirationSeconds: 3607
            path: token
        - configMap:
            items:
            - key: ca.crt
              path: ca.crt
            name: kube-root-ca.crt
        - downwardAPI:
            items:
            - fieldRef:
                apiVersion: v1
                fieldPath: metadata.namespace
              path: namespace
  volumeMounts:
    - mountPath: /var/run/secrets/kubernetes.io/serviceaccount
      name: kube-api-access
      readOnly: true

spark:
  serviceAccount:
    automountServiceAccountToken: false

webhook:
  serviceAccount:
    automountServiceAccountToken: false
  volumes:
    - name: kube-api-access
      projected:
        defaultMode: 420
        sources:
        - serviceAccountToken:
            expirationSeconds: 3607
            path: token
        - configMap:
            items:
            - key: ca.crt
              path: ca.crt
            name: kube-root-ca.crt
        - downwardAPI:
            items:
            - fieldRef:
                apiVersion: v1
                fieldPath: metadata.namespace
              path: namespace
  volumeMounts:
    - mountPath: /var/run/secrets/kubernetes.io/serviceaccount
      name: kube-api-access
      readOnly: true

[ImpSy]

/lgtm

[Aransh]

/assign @ChenYi015

[google-oss-prow]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: ChenYi015, ImpSy, malki-akamai

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[ChenYi015]

/lgtm