Include clusterName in the OBI getting started documentation (#2367)

* Include clusterName in the OBI getting started docs

* Clarify when clusterName is needed

* Apply feedback

Author: MrAlias

docs/zero-code-ebpf-instrumentation.md

@@ -42,12 +42,24 @@ helm install my-splunk-otel-collector \
   splunk-otel-collector-chart/splunk-otel-collector \
   --set="splunkObservability.realm=${SPLUNK_REALM}" \
   --set="splunkObservability.accessToken=${SPLUNK_ACCESS_TOKEN}" \
+  --set="clusterName=${CLUSTER_NAME}" \
   --set="obi.enabled=true"
 ```
 
+The chart can auto-detect `k8s.cluster.name` when `distribution` is set to one
+of the supported values for auto-discovery: `eks`, `eks/auto-mode`, `gke`,
+`gke/autopilot`, or `openshift`. `eks/fargate` is an exception and still
+requires `clusterName` to be set explicitly. For other distributions, set
+`clusterName` explicitly.
+
 ### Configuration Options
 
-For basic usage, no additional configuration is required.
+For basic usage, enable OBI with `obi.enabled=true` and make sure the chart can
+set `k8s.cluster.name` either by:
+
+- Setting `clusterName` explicitly
+- Setting `distribution` to `eks`, `eks/auto-mode`, `gke`, `gke/autopilot`, or
+  `openshift` so the chart can auto-detect it
 
 Additional configuration options are available to customize OBI features.
 Refer to the [OBI chart's documentation] for more details.

examples/ebpf-instrumentation/README.md

@@ -20,6 +20,11 @@ helm install splunk-otel-collector splunk-otel-collector-chart/splunk-otel-colle
   --set="environment=<ENVIRONMENT>"
 ```
 
+`clusterName` can be omitted only when `distribution` is set to a value that
+supports auto-discovery of `k8s.cluster.name`: `eks`, `eks/auto-mode`, `gke`,
+`gke/autopilot`, or `openshift`. `eks/fargate` is an exception and still
+requires `clusterName` to be set explicitly.
+
 Refer to OBI [documentation for deployment on AKS/EKS](https://opentelemetry.io/docs/zero-code/obi/security/#deploy-on-akseks) if needed.
 
 [platform requirements]: ../../docs/zero-code-ebpf-instrumentation.md#platform-requirements