Feature: Export OIDC from Managed Cluster

[theunrepentantgeek]

A ManagedCluster may optionally define an OIDC issuer for use with Federated Identity. We should allow publication of this value to a config-map to allow dynamic use by other resources.

See the property oidcIssuerProfile and the underlying type ManagedClusterOIDCIssuerProfile . The URL is available as issuerURL on the status.

(Requested in #2950 as an example of a wider requirement.)

[matthchr]

There's also a way to get this for the current cluster you're in, if you're in a cluster which is OIDC enabled. That has benefits if you want the FederatedIdentityCredential to apply on the cluster you're on (which you probably want to)