Cluster admin access via exposed local JWT

Authorization flaw in assisted-service in Red Hat multicluster engine for Kubernetes allows remote authenticated users to read kubeadmin credentials. In AUTH_TYPE=local mode, the local authenticator grants full administrative access to any request bearing a valid JWT, and the cluster credentials and kubeconfig download endpoints apply no narrower per-endpoint authorization. On on-premises ACM and MCE hubs, any user who can read an InfraEnv object in a namespace can extract the plaintext JWT from InfraEnvStatus.ISODownloadURL and use it to retrieve kubeadmin passwords and kubeconfigs for arbitrary provisioned spoke clusters.