Uploads an attachment. For an example, see Upload media as a file attachment. Requires user authentication with one of the following authorization scopes: - https://www.googleapis.com/auth/chat.messages.create - https://www.googleapis.com/auth/chat.messages - https://www.googleapis.com/auth/chat.import (import mode spaces only) You can upload attachments up to 200 MB. Certain file types aren't supported. For details, see File types blocked by Google Chat.