RHIDP-4566: document how to manage PVCs in RHDH operator

Author: hmanwani-rh

modules/admin/proc-rhdh-deployment-config.adoc

@@ -46,8 +46,10 @@ spec:
 ----
 
 `volumes`::
-Add an additional volume named `my-volume` and mount it under `/my/path` in the {product-short} application container.
 +
+--
+Add an additional volume named `my-volume` and mount it under `/my/path` in the {product-short} application container.
+
 .Example additional volume
 [source, yaml]
 ----
@@ -73,9 +75,9 @@ spec:
                       storageClassName: "special"
                 name: my-volume
 ----
-+
+
 Replace the default `dynamic-plugins-root` volume with a persistent volume claim (PVC) named `dynamic-plugins-root`. Note the `$patch: replace` directive, otherwise a new volume will be added.
-+
+
 .Example `dynamic-plugins-root` volume replacement
 [source, yaml]
 ----
@@ -96,6 +98,59 @@ spec:
                   claimName: dynamic-plugins-root
 ----
 
+Starting from v1alpha3 (Operator version 0.4.0), you can mount directories from pre-created PVCs using the `spec.application.extraFiles.pvcs` field. PVCs are mounted as directories to the container's path, based on the following logic:
+
+* If `spec.application.extraFiles.pvcs[].mountPath` is defined, the PVC is mounted to the specified path.
+* If `spec.application.extraFiles.pvcs[].mountPath` is not defined, the PVC is mounted under `spec.application.extraFiles.mountPath/`.
+* If neither is defined, the PVC defaults to `/opt/app-root/src`.
+
+.Example PVC objects in the namespace
+[source,yaml]
+----
+apiVersion: v1
+kind: PersistentVolumeClaim
+metadata:
+  name: myclaim1
+spec:
+  accessModes:
+    - ReadWriteOnce
+  resources:
+    requests:
+      storage: 2Gi
+---
+apiVersion: v1
+kind: PersistentVolumeClaim
+metadata:
+  name: myclaim2
+spec:
+  accessModes:
+    - ReadWriteOnce
+  resources:
+    requests:
+      storage: 2Gi
+----
+
+The PVCs in the previous example can be mounted to the container as follows:
+
+.Example PVCs mounted to the container
+[source,yaml]
+----
+spec:
+  application:
+    extraFiles:
+      mountPath: /my/path
+      pods:
+        - name: myclaim1
+        - name: myclaim2
+          mountPath: /vol/my/claim
+----
+
+As a result, the following directories are mounted in the container:
+
+* `/my/path/myclaim1`
+* `/vol/my/claim`
+--
+
 `cpu` request::
 
 Set the CPU request for the {product-short} application container to 250m.