Add example with 'for' for prometheus additional custom rules

[hensg]

Suggestion: add the for keyword in the example and how to use it for additional kubernetes rules.

Example from examples/folder:

local kp = (import 'kube-prometheus/main.libsonnet') + {
  values+:: {
    common+: {
      namespace: 'monitoring',
    },
  },
  exampleApplication: {
    prometheusRuleExample: {
      apiVersion: 'monitoring.coreos.com/v1',
      kind: 'PrometheusRule',
      metadata: {
        name: 'my-prometheus-rule',
        namespace: $.values.common.namespace,
      },
      spec: {
        groups: [
          {
            name: 'example-group',
            rules: [
              {
                alert: 'ExampleAlert',
                expr: 'vector(1)',               
                labels: {
                  severity: 'warning',
                },
                annotations: {
                  description: 'This is an example alert.',
                },
              },
            ],
          },
        ],
      },
    },
  },
};

{ ['00namespace-' + name]: kp.kubePrometheus[name] for name in std.objectFields(kp.kubePrometheus) } +
{ ['0prometheus-operator-' + name]: kp.prometheusOperator[name] for name in std.objectFields(kp.prometheusOperator) } +
{ ['node-exporter-' + name]: kp.nodeExporter[name] for name in std.objectFields(kp.nodeExporter) } +
{ ['kube-state-metrics-' + name]: kp.kubeStateMetrics[name] for name in std.objectFields(kp.kubeStateMetrics) } +
{ ['alertmanager-' + name]: kp.alertmanager[name] for name in std.objectFields(kp.alertmanager) } +
{ ['prometheus-' + name]: kp.prometheus[name] for name in std.objectFields(kp.prometheus) } +
{ ['prometheus-adapter-' + name]: kp.prometheusAdapter[name] for name in std.objectFields(kp.prometheusAdapter) } +
{ ['grafana-' + name]: kp.grafana[name] for name in std.objectFields(kp.grafana) } +
{ ['example-application-' + name]: kp.exampleApplication[name] for name in std.objectFields(kp.exampleApplication) }

What I tried to do by add the for:

local kp = (import 'kube-prometheus/main.libsonnet') + {
  values+:: {
    common+: {
      namespace: 'monitoring',
    },
  },
  exampleApplication: {
    prometheusRuleExample: {
      apiVersion: 'monitoring.coreos.com/v1',
      kind: 'PrometheusRule',
      metadata: {
        name: 'my-prometheus-rule',
        namespace: $.values.common.namespace,
      },
      spec: {
        groups: [
          {
            name: 'example-group',
            rules: [
              {
                alert: 'ExampleAlert',
                expr: 'vector(1)',   
                for: '5m',            
                labels: {
                  severity: 'warning',
                },
                annotations: {
                  description: 'This is an example alert.',
                },
              },
            ],
          },
        ],
      },
    },
  },
};

{ ['00namespace-' + name]: kp.kubePrometheus[name] for name in std.objectFields(kp.kubePrometheus) } +
{ ['0prometheus-operator-' + name]: kp.prometheusOperator[name] for name in std.objectFields(kp.prometheusOperator) } +
{ ['node-exporter-' + name]: kp.nodeExporter[name] for name in std.objectFields(kp.nodeExporter) } +
{ ['kube-state-metrics-' + name]: kp.kubeStateMetrics[name] for name in std.objectFields(kp.kubeStateMetrics) } +
{ ['alertmanager-' + name]: kp.alertmanager[name] for name in std.objectFields(kp.alertmanager) } +
{ ['prometheus-' + name]: kp.prometheus[name] for name in std.objectFields(kp.prometheus) } +
{ ['prometheus-adapter-' + name]: kp.prometheusAdapter[name] for name in std.objectFields(kp.prometheusAdapter) } +
{ ['grafana-' + name]: kp.grafana[name] for name in std.objectFields(kp.grafana) } +
{ ['example-application-' + name]: kp.exampleApplication[name] for name in std.objectFields(kp.exampleApplication) }

Error: object comprehension can only have one field.

Reason: took me a few hours to realize what was going on and why the jsonnet was throwing errors when I attempted to add for keyword in the example below.

Solution: add quotes to the for keyword, so it is not interpreted in the function for name in std.objectFields... as a language keyword command.

   ...
   expr: 'vector(1)',
   'for': '5m',
   labels: {
   ...