Sets device-level attributes, such as a deviceId or an iOS push token, for the current device. If the device is shared between multiple users, pass a userId with the deviceId to update the device for each user. (Passing just the deviceId will only update it once). If the device already exists, the attributes will be updated. If the device and user do not exist, a new user will be created along with this device (see the createDisposition option below). See selecting a user for more.
At least one of the following must be set to create/update a device: appVersion, systemName, systemVersion, browserName, browserVersion, deviceName, deviceModel, iosPushToken, gcmRegistrationId, or webPushSubscription.