Test and Document Utilizing argocd oidc.config rootCA option

Currently to get ArgoCD to trust a custom CertificateAuthority for OIDC connections we added this workaround to mount and have the pod trust the CA

They now appear to have an option for rootCA in PEM format that gets fed into the config.oidc.config values we already utilize under an sso: value: https://argo-cd.readthedocs.io/en/stable/operator-manual/user-management/#configuring-a-custom-root-ca-certificate-for-communicating-with-the-oidc-provider

Test and document (if successful) BigBang's sso.certificate_authority passing through to this rootCA value if present in BigBang and confirm that argocd SSO still works as expected.

• rootCA value passthrough added
• Documentation in docs/keycloak.md updated if successful