setDeviceToken
Set the device token for push notifications. This method should be called when the device token changes. It updates the token locally and on the server using the specific PushHandler for the credential's platform. If it fails to update the token locally, the method will not attempt to update it on the server.
Return
A Result containing a Boolean indicating success or an Exception in case of failure.
Parameters
deviceToken
The new device token for push notifications.
credentialId
Optional ID of a specific credential to update the token for. When null, updates the token globally for all credentials.