helm: make it possible to override `-prefix=nats` for the exporter

[bbigras]

-prefix=nats is hard codded here:

https://github.com/nats-io/k8s/blob/88dcf6eefbc6a7cd41fe1ba4374f977a52e05cc5/helm/charts/nats/templates/statefulset.yaml#L542

but it seems that gnatsd is normally the default and used in public dashboards:

https://github.com/nats-io/prometheus-nats-exporter/blob/9468d46771d476bb896f8be95d3101558fa9f466/walkthrough/grafana-nats-dash.json#L246-L249

https://github.com/kubenav/deploy/blob/ed66ab3bf470fe7a43c6990e39d158b249f5ff7c/dashboards/nats-dashboard.yaml#L23

[bbigras]

meanwhile I'm using this:

kustomization.yaml

helmCharts:
- name: nats
  repo: https://nats-io.github.io/k8s/helm/charts/
  version: v0.17.0
  releaseName: nats
  namespace: default
  valuesFile: ./values.yaml

patches:
- ./patch.yaml

patch.yaml

apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: nats
  namespace: default
spec:
  template:
    spec:
      containers:
      - args:
        - -connz
        - -routez
        - -subz
        - -varz
        - -prefix=gnatsd
        - -use_internal_server_id
        - -jsz=all
        - http://localhost:8222/
        name: metrics

[caleblloyd]

Supported via patching/merging in nats-1.0.0-beta.0