I guess that you are using the master snapshot of Secure Social. This means that any changes in the central repo will be downloaded when you build.
The latest changes to the master snapshot is this: Renamed id field in Identity to identityId (breaks backwards compatibility).
So your code should be
case class WithProvider(provider: String) extends Authorization {
def isAuthorized(user: Identity) = {
user.identityId.providerId == provider
}
}