Project: mesos
Issue MESOS-3867: Make `Resource.DiskInfo.Persistence.principal` a required field
A `principal` field is being added to the `Resource.DiskInfo.Persistence` message to facilitate authorization of persistent volume creation/deletion. In the long-run it should be a required field, but it's being initially introduced as optional to avoid breaking existing frameworks. The field should be changed to required at the end of a deprecation cycle.
Story points: 1