Is your feature request related to a problem? Please describe.

We want to create BQ datasets and set the storage billing model property to PHYSICAL, but it doesn't look like this option is available using the latest release.

Describe the solution you'd like

We would like a StorageBillingModel field to be added to the bigquery.DatasetMetadata struct so we can create datasets with Physical billing storage model.

Describe alternatives you've considered

We are currently using this SDK and would rather not resort to calling the BQ REST API by ourselves...