feat(securityContext): Add the ability to set securityContext values

[bryopsida]

What this PR does / why we need it:

Adds the capability to set securityContext values at the pod and container levels. This is needed in order to deploy into a namespace with PSA enforcing at the restricted level.

Special notes for your reviewer:

Tested with the following labels set on namespace.

  labels:
    kubernetes.io/metadata.name: couchdb-test
    pod-security.kubernetes.io/audit: restricted
    pod-security.kubernetes.io/enforce: restricted
    pod-security.kubernetes.io/warn: restricted

And the following overrides

podSecurityContext:
  seccompProfile:
   type: RuntimeDefault
  fsGroup: 5984
  fsGroupChangePolicy: "Always"
containerSecurityContext:
  runAsNonRoot: true
  runAsUser: 5984
  runAsGroup: 5984
  allowPrivilegeEscalation: false
  capabilities:
    drop:
      - ALL

Pods passed PSA enforcement and entered a ready state.

These values are optional and if users do not provide overrides for these values there will be no change to existing installs/releases.

Checklist

[Place an '[x]' (no spaces) in all applicable fields. Please remove unrelated fields.

• Chart Version bumped
• e2e tests pass
• Variables are documented in the README.md

[willholley]

thanks @bryopsida - looks like a good change to me. I wonder whether we'd want to default to these securityContext values assuming they are compatible with the official images, though that's probably one for a major release.