public byte[] toJson() {
        try {
            Slime slime = new Slime();
            toSlime(slime.setObject());
            return SlimeUtils.toJsonBytes(slime);
        }
        catch (IOException e) {
            throw new RuntimeException("Serialization of session data to json failed", e);
        }
    }
Data class for session information, typically parameters supplied in a deployment request that needs
to be persisted in ZooKeeper. These will be used when creating a new session based on an existing one.

@author hmusum
configserver/src/main/java/com/yahoo/vespa/config/server/session/SessionData.java