GDB-10532: Added configuration examples for GraphDB virtualization features

examples/virtualization/README.md

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+# GraphDB Virtualization Examples
+
+This folder contains examples of how to configure GraphDB's virtualization features by providing JDBC drivers to GraphDB's classpath.
+See https://graphdb.ontotext.com/documentation/10.7/virtualization.html for more information and [Ontop](https://ontop-vkg.org/guide/)
+configuration examples.
+
+## Using GraphDB Persistence
+
+For GraphDB to pick up and use JDBC drivers, their JAR files must be registered in the classpath.
+The Helm chart configures GraphDB to expect JDBC drivers at `/opt/graphdb/home/jdbc-driver` from where the database will pick them up.
+This detection is dynamic so you don't need to restart GraphDB when provisioning drivers.
+
+The directory `/opt/graphdb/home/jdbc-driver` is located inside the default persistence volume.
+JDBC drivers that have been provisioned in this directory will be available between pod restarts and GraphDB updates.
+
+There are two common ways to provide drivers inside existing PV:
+
+* Using a custom init container that will download JDBC jars from the internet.
+* Copying the files manually using `kubectl` or from another PV.
+
+This example will focus on copying JAR files with `kubectl`.
+
+For example, to configure GraphDB with a JDBC driver for PostgreSQL inside the GraphDB pod `graphdb-0`, you can use:
+
+```bash
+kubectl cp postgresql-42.7.4.jar graphdb-0:/opt/graphdb/home/jdbc-driver/
+```
+
+In case of a GraphDB cluster setup, you have to provide the driver to all pods:
+
+```bash
+kubectl cp postgresql-42.7.4.jar graphdb-0:/opt/graphdb/home/jdbc-driver/
+kubectl cp postgresql-42.7.4.jar graphdb-1:/opt/graphdb/home/jdbc-driver/
+kubectl cp postgresql-42.7.4.jar graphdb-2:/opt/graphdb/home/jdbc-driver/
+```
+
+## Using Another Persistence Volume
+
+Another option is to prepare a different PVC and PV, copy the JDBC drivers inside that PV and configure GraphDB to use this with:
+
+```yaml
+extraVolumes:
+  - name: jdbc-drivers
+    persistentVolumeClaim:
+      claimName: jdbc-drivers
+
+extraVolumeMounts:
+  - name: jdbc-drivers
+    mountPath: /opt/graphdb/home/jdbc-driver
+```