now `beta` and enabled by default. When enabled, legacy auto-generated service account token secrets are auto-labeled with a `kubernetes.io/legacy-token-invalid-since` label if the credentials have not been used in the time specified by `--legacy-service-account-token-clean-up-period` (defaulting to one year), **and** are referenced from the `.secrets` list of a ServiceAccount object, **and**  are not referenced from pods. This label causes the authentication layer to reject use of the credentials....