Editor can forge file-provisioning provenance on dashboards via the dashboard API

An Editor can set file-provisioning metadata (the grafana.app/managedBy, grafana.app/managerId and grafana.app/sourcePath annotations) when creating a dashboard through the dashboard API, because these fields were stored without an authorization check. The dashboard then appears file-provisioned, and administrators can no longer update or delete it through Grafana. The impact is limited to the same organization and no data is exposed.