See also:
https://cloud.google.com/pubsub/access_control PubSub Access Control Documentation
See also:
https://cloud.google.com/pubsub/docs/reference/rest/v1/projects.topics/getIamPolicy Get Topic IAM Policy
See also:
https://cloud.google.com/pubsub/docs/reference/rest/v1/projects.topics/setIamPolicy Set Topic IAM Policy
See also:
https://cloud.google.com/pubsub/docs/reference/rest/v1/projects.topics/testIamPermissions Test Topic Permissions