adding docs for custom plugin images (#394)

Author: jaidevmane

README.md

@@ -21,6 +21,7 @@
     4. [Self-Signed Certificate](docs/config/self_signed_certs.md)
     5. [Use NooBaa as a Backup Storage Location](docs/config/noobaa/install_oadp_noobaa.md) 
     6. [Use Velero --features flag](docs/config/features_flag.md)
+    6. [Use Custom Plugin Images for Velero ](docs/config/custom_plugin_images.md)
 6. [Upgrade from 0.2](docs/upgrade.md)
 7. Examples
     1. [Stateless App Backup/Restore](docs/examples/stateless.md)

docs/config/custom_plugin_images.md

@@ -0,0 +1,50 @@
+<hr style="height:1px;border:none;color:#333;">
+<h1 align="center">Usage of Custom Plugin Images for Velero</h1>
+<hr style="height:1px;border:none;color:#333;">
+
+The OADP Operator supports custom plugin images under the `unsupportedOverrides` field as detailed in the YAML below. This feature can be used to support rapid development and testing of custom images for supported plugins and provides a way for developers to quickly deploy and test their changes.
+
+Details for supported plugins and thier usage is given below, and please use the respective keys for the plugins. All keys must be entered in the Velero CR under a new field called as `unsupportedOverrides`, and with the key below for reference and corresponding image tag as their value.
+
+
+ - Velero Imagekey  -> `veleroPluginImageFqin`
+ - AWS Plugin ImageKey  -> `awsPluginImageFqin`
+ - OpenShift Plugin ImageKey  -> `openshiftPluginImageFqin`
+ - Azure Plugin ImageKey -> `azurePluginImageFqin`
+ - GCP Plugin ImageKey  -> `gcpPluginImageFqin`
+ - CSI Plugin ImageKey  -> `csiPluginImageFqin`
+ - Restic Restore ImageKey -> `resticRestoreImageFqin`
+
+Below is an example Velero CR with the unsupportedOverrides key added for reference. Please note that the `<IMAGE_PLACEHOLDER WITH TAG>` is to be replaced with the plugin image and tag.
+
+```
+apiVersion: oadp.openshift.io/v1alpha1
+kind: Velero
+metadata:
+  name: velero-sample
+spec:
+  defaultVeleroPlugins:
+  - aws
+  backupStorageLocations:
+  - name: default
+    provider: aws
+    default: true
+    objectStorage:
+      bucket: my-bucket
+      prefix: my-prefix
+    config:
+      region: us-east-1
+      profile: "default"
+    credential:
+      name: cloud-credentials
+      key: cloud
+  volumeSnapshotLocations:
+  - name: default
+    provider: aws
+    config:
+      region: us-west-2
+      profile: "default"
+  unsupportedOverrides:
+    awsPluginImageFqin: <IMAGE_PLACEHOLDER WITH TAG>
+    openshiftPluginImageFqin: <IMAGE_PLACEHOLDER WITH TAG>
+```