private ApplicationLock lockApplication(Optional<ApplicationId> applicationId) {
        return applicationId.map(id -> new ApplicationLock(Optional.of(applicationRepo.lock(id))))
                .orElseGet(() -> new ApplicationLock(Optional.empty()));
    }
A session for which we don't have a watcher, i.e. hitherto unknown to us.

@param sessionId session id for the new session
configserver/src/main/java/com/yahoo/vespa/config/server/session/SessionRepository.java