Allow admins to modify updatedOn date

[kevinhinterlong]

By default the updatedOn date should be the last change, but it would be useful to keep it the same for migration purposes if manually specified https://github.com/yavin-dev/framework/blob/3a7ab53705ca16f30e9a66b00c50e94c3c99fbb4/packages/webservice/models/src/main/kotlin/com/yahoo/navi/ws/models/beans/Asset.kt#L51-L52