Cert-manager managed CA certificate Duration & ExpiryWindow

[mekaan]

Request

We request the ability to modify the CA certificate's Duration and ExpiryWindow in the Helm chart, similar to how we can modify these values for node and client certificates.

Why this feature is needed

The default duration is 90 days. When the node certificates have a duration exceeding 90 days, the nodes fail to authenticate because the CA certificate used to create them must remain valid for the node certificate to be valid. Therefore, it is essential to have a CA certificate duration longer than the node certificate duration. Since the default value for node certificate duration is 8760h, they become invalid before getting expire. This feature is necessary to ensure seamless authentication without any manual intervention.