@Serial
    private void writeObject(final ObjectOutputStream out) throws IOException {
        out.writeUTF(toString());
    }
Parse.

@param key the key
@return the client flow execution key
@throws BadlyFormattedFlowExecutionKeyException the badly formatted flow execution key exception
core/cas-server-core-webflow-api/src/main/java/org/apereo/cas/web/flow/executor/ClientFlowExecutionKey.java