static String toString(NodeType type) {
        return switch (type) {
            case tenant -> "tenant";
            case host -> "host";
            case proxy -> "proxy";
            case proxyhost -> "proxyhost";
            case config -> "config";
            case confighost -> "confighost";
            case controller -> "controller";
            case controllerhost -> "controllerhost";
        };
    }
Returns the event type, or null if this event type should be ignored
node-repository/src/main/java/com/yahoo/vespa/hosted/provision/persistence/NodeSerializer.java