registerDevice

Registers this device's authentication public key with the server (docs/server-authentication.md), in a request signed with that key. Needed once before publishPreKeys and receive; calling it again is safe. Throws SecureMessageTransportException.DeviceRegistrationConflict if the server has another key for localAddress; there is no reset. The first registration of an address needs the host application's authorization on the server (S1; SecureMessageTransportException.DeviceRegistrationNotAuthorized).