Securely send a notification to a specific device. Data in securedData filed is encrypted before sending.
The device field can be refered by its deviceId or externalId, this can be set with idType parameter, which is deviceId by default.
If externalId is used, it will be sent to all enabled devices sharing the same externalId.
"device" : "deviceId1"
"device" : "externalId1"