docs: Document how to ship OTEL traces

Author: sbernauer

docs/modules/opa/pages/usage-guide/OpenTelemetry.adoc

@@ -0,0 +1,30 @@
+= OpenTelemetry
+:description: Ship OPA traces and logs to OpenTelemetry
+:opa-docs: https://v1-4-2--opa-docs.netlify.app/configuration/#distributed-tracing
+
+Opa supports sending OpenTelemetry traces as stated in {opa-docs}[the documentation].
+
+As of SDP 25.7 we don't support `configOverrides`.
+To enable traces you need to modify the config and thus xref:opa:usage-guide/operations/cluster-operations.adoc[pause the reconciliation] of your OpaCluster, so that changes to the ConfigMap aren't immediately overridden by the opa-operator.
+
+WARNING: It's not encouraged to pause the reconciliation longer than temporary. We recommend disabling it while you debug e.g. performance problems and re.enabling it afterwards. This problem will be solved once we support configOverrides for OPA.
+
+Afterwards you can edit the `<stacklet-name>-server-default` ConfigMap and append a `distributed_tracing` section as follows.
+Please check the {opa-docs}[OPA documentation] on how other settings you can configure.
+
+[source,yaml]
+----
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: opa-server-default
+data:
+  config.json: |-
+    {
+      <<< existing JSON >>>
+      "distributed_tracing": {
+        "address": "jaeger-collector.default.svc.cluster.local:4317",
+        "type": "grpc"
+      }
+    }
+----

docs/modules/opa/pages/usage-guide/configuration-environment-overrides.adoc

@@ -8,7 +8,7 @@ This will lead to faulty installations.
 
 == Configuration properties
 
-Currently, not supported for `config.yaml`.
+Currently, not supported for `config.json`.
 
 == Environment variables
 

docs/modules/opa/partials/nav.adoc

@@ -8,6 +8,7 @@
 ** xref:opa:usage-guide/resources.adoc[]
 ** xref:opa:usage-guide/logging.adoc[]
 ** xref:opa:usage-guide/monitoring.adoc[]
+** xref:opa:usage-guide/OpenTelemetry.adoc[]
 ** xref:opa:usage-guide/configuration-environment-overrides.adoc[]
 ** xref:opa:usage-guide/operations/index.adoc[]
 *** xref:opa:usage-guide/operations/cluster-operations.adoc[]