REQUIRED: The Cloud Spanner resource for which the policy is being set. The format is projects/<project ID>/instances/<instance ID> for instance resources and projects/<project ID>/instances/<instance ID>/databases/<database ID> for databases resources.
The request body contains data with the following structure:
REQUIRED: The complete policy to be applied to the resource. The size of the policy is limited to a few 10s of KB. An empty policy is a valid policy but certain Google Cloud services (such as Projects) might reject them.
If successful, the response body contains an instance of Policy.