The request for [RestoreDatabase][google.spanner.admin.database.v1.Dat
abaseAdmin.RestoreDatabase].
Required. The id of the database to create and restore to.
This database must not already exist. The database_id
appended to parent forms the full database name of the
form projects/<project>/instances/<instance>/databases/<data
base_id>.
Name of the backup from which to restore. Values are of the
form
projects/<project>/instances/<instance>/backups/<backup>.