doc: Add logging documentation

Author: siegfriedweber

docs/modules/opensearch/pages/usage-guide/logging.adoc

@@ -0,0 +1,34 @@
+= Log aggregation
+:description: The logs can be forwarded to a Vector log aggregator by providing a discovery ConfigMap for the aggregator and by enabling the log agent.
+
+The logs can be forwarded to a Vector log aggregator by providing a discovery ConfigMap for the aggregator and by enabling the log agent:
+
+[source,yaml]
+----
+spec:
+  clusterConfig:
+    vectorAggregatorConfigMapName: vector-aggregator-discovery
+  nodes:
+    config:
+      logging:
+        enableVectorAgent: true
+        containers:
+          opensearch:
+            console:
+              level: INFO
+            file:
+              level: INFO
+            loggers:
+              ROOT:
+                level: INFO
+          vector:
+            console:
+              level: INFO
+            file:
+              level: INFO
+            loggers:
+              ROOT:
+                level: INFO
+----
+
+Further information on how to configure logging, can be found in xref:concepts:logging.adoc[].

docs/modules/opensearch/partials/nav.adoc

@@ -7,6 +7,7 @@
 ** xref:opensearch:usage-guide/storage-resource-configuration.adoc[]
 ** xref:opensearch:usage-guide/configuration-environment-overrides.adoc[]
 ** xref:opensearch:usage-guide/monitoring.adoc[]
+** xref:opensearch:usage-guide/logging.adoc[]
 ** xref:opensearch:usage-guide/operations/index.adoc[]
 *** xref:opensearch:usage-guide/operations/cluster-operations.adoc[]
 *** xref:opensearch:usage-guide/operations/pod-placement.adoc[]