BatchDelete: Deletes multiple attachments on a given beacon. This operation is permanent and cannot be undone. You can optionally specify `namespacedType` to choose which attachments should be deleted. If you do not specify `namespacedType`, all your attachments on the given beacon will be deleted. You also may explicitly specify `*/*` to delete all. Authenticate using an [OAuth access token](https://developers.google.com/identity/protocols/OAuth2) from a signed-in user with **Is owner** or **Can edit** permissions in the Google Developers Console project.