Create a new DehydratedDevice which can be uploaded to the server.
Clear the dehydrated device key saved in the crypto store.
Get the cached dehydrated device key if any.
None if the key was not previously cached (via DehydratedDevices.saveDehydratedDeviceKey).
None
Rehydrate a dehydrated device.
Store the dehydrated device key in the crypto store.
Create a new DehydratedDevice which can be uploaded to the server.