Storing the email should not be an explicit part of the SPASpec/credentials. The credentials should a blob that is handled exclusively by the SPA for the purposes of storing whatever data it requires to function.

The email (or user id) should be returned from the SPA via the `connected` message as per the API.

In the case of the Talkilla SPA, the login success may store the email address in the credentials, but the UI won't know about it until it gets that `connected` message back.