static String toString(Node.State state) {
        return switch (state) {
            case active -> "active";
            case dirty -> "dirty";
            case failed -> "failed";
            case inactive -> "inactive";
            case parked -> "parked";
            case provisioned -> "provisioned";
            case ready -> "ready";
            case reserved -> "reserved";
            case deprovisioned -> "deprovisioned";
            case breakfixed -> "breakfixed";
        };
    }
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