zrok/docs/guides/v0.4_metrics.md

`v0.4` includes a new metrics infrastructure based on OpenZiti usage, which provides `zrok` with telemetry used to power end-user intelligence about shares, and also to power usage-based limits.

# Configuration

This requires a version of OpenZiti with a `fabric` dependency of `v0.22.52` or newer.

## controller configuration:

```
network:
  intervalAgeThreshold: 5s 
  metricsReportInterval: 5s

events:
  jsonLogger:
    subscriptions:
      - type: fabric.usage
        version: 3
    handler:
      type: file
      format: json
      path: /tmp/fabric-usage.log
```

## router configuration:

```
metrics:
  reportInterval: 5s
  intervalAgeThreshold: 5s
```