Failed to validate plan: spec.window is invalid

Version v0.15.0-rc1

Describe the bug I have updated the system-update-controller in my cluster to v0.15.0-rc1 by applying the system-upgrade-controller.yaml and crd.yaml of version v0.15.0-rc1.

After that I have added this in the spec: section of my Plan (as mentioned by @brandond here rancher/system-upgrade-controller#335 ):

    window:
        days:
            - "saturday"
        startTime: "00:15"
        endTime: "06:15"
        timeZone: "Europe/Berlin"

But when I apply the plan I get this warning in the system-update-controller pod logs:

"Event occurred" object="system-upgrade/k3s-agent" fieldPath="" kind="Plan" apiVersion="upgrade.cattle.io/v1" 
type="Warning" reason="ValidateFailed" message="Failed to validate plan: spec.window is invalid"