init container for oidc discovery

[MartinLoeper]

It would be nice if the helm chart would provide the option to inject an init container which waits until the oidc discovery endpoint is up and running.

Otherwise, harbor might start and if the oidc discovery endpoint is temporary not available, harbor will disable the OIDC login button. The discovery is also not retried by the harbor core. This is highly confusing as one would expect better resiliency during harbor startup.

This issue could be solved either in the harbor core or in the helm chart I guess.