@Override
    public boolean isEncrypted() {
        return Optional.ofNullable(conn)
            .map(Connection::isEncrypted)
            .orElse(Boolean.FALSE);
    }
Returns a text with the available stream features. Each subclass may return different
values depending whether the session has been authenticated or not.

@return a text with the available stream features or {@code null} to add nothing.
xmppserver/src/main/java/org/jivesoftware/openfire/session/LocalSession.java