Export parameter to override volumes's storageClass created during export

Kasten K10 provides an option to use an override setting in the policy to specify a storageClass that are created and used during exports.

ExporterStorageClassName parameter can be used for namespaces that have PVCs using a single storageClass and also in the case of multiple PVCs using different storageClasses in the same namespace.

This is particularly helpful when the application PVC is provisioned using a storageClass set to `Retain` in the deletion policy. This setting will make sure that there wouldn't be any PV left in released state when the temporary PVCs created for exports are cleaned up.

The examples below show how to add these parameters by editing the Policy manually.

Single storageClass:

apiVersion: config.kio.kasten.io/v1alpha1

kind: Policy

metadata:

 name: postgresql-backup-1

 namespace: kasten-io

spec:

 actions:

 - action: backup

 - action: export

   exportParameters:

     exportData:

       enabled: true

       # Storage class to use for any temporary PVCs created

       # during the snapshot conversion process. If not specified, the

       # storage class of the source volume is used.

       exporterStorageClassName: gp2-delete

     frequency: '@hourly'

     migrationToken:

       name: postgresql-backup-1-migration-token-7vrgc

       namespace: kasten-io

     profile:

       name: test-jai

       namespace: kasten-io

     receiveString: xxxxxxx

   retention: {}

 createdBy: kasten-io:k10-k10

 frequency: '@hourly'

 retention:

   daily: 7

   hourly: 24

   monthly: 12

   weekly: 4

   yearly: 7

 selector:

   matchExpressions:

   - key: k10.kasten.io/appNamespace

     operator: In

     values:

     - postgresql

     - kasten-io-cluster

Multiple storageClass:

apiVersion: config.kio.kasten.io/v1alpha1

kind: Policy

metadata:

 name: postgresql-backup-1

 namespace: kasten-io

spec:

 actions:

 - action: backup

 - action: export

   exportParameters:

     exportData:

       enabled: true

       overrides:

           # Override setting of a specific storage class

         - storageClassName: gp2-retain

           enabled: true

           exporterStorageClassName: gp2-delete

         - storageClassName: gp3-retain

           enabled: true

           exporterStorageClassName: gp3-delete

           # Setting to disable the export for a specific storageClass

         - storageClassName: nfs-client

           enabled: false

     frequency: '@hourly'

     migrationToken:

       name: postgresql-backup-1-migration-token-7vrgc

       namespace: kasten-io

     profile:

       name: test-jai

       namespace: kasten-io

     receiveString: xxxxxxx

   retention: {}

 createdBy: kasten-io:k10-k10

 frequency: '@hourly'

 retention:

   daily: 7

   hourly: 24

   monthly: 12

   weekly: 4

   yearly: 7

 selector:

   matchExpressions:

   - key: k10.kasten.io/appNamespace

     operator: In

     values:

     - postgresql

     - kasten-io-cluster

 # Setting to disable the export for a specific storageClass

         - storageClassName: nfs-client

           enabled: false

Regarding all fields that can be configured with the policy API, please refer to https://docs.kasten.io/latest/api/policies.html for more information.