I am trying to implement a signup mechanism similar to the WhatsApp’s where user does not enter username or password etc. User needs to submit the verification code which is sent from the server to verify his phone number. Then, I check if the entered code matches with the phone number and call Accounts.createUser(). Now what should I do to authenticate and log the user into app, immediately after submission of the correct code? I know it is done via tokens but how in Meteor Accounts?