feat(bdc): update bdc builder with adding tag (#36)

Ref: openebs-archive/maya#1648

A new label fixed selector (openebs.io/block-device-tag)
has been added to BDC to help with narrowing down the
block devices that can be claimed via the BDC.

This will allow users to tag block devices
and indicate which tagged devices can be used
by the BDC.

Signed-off-by: kmova <kiran.mova@mayadata.io>

pkg/apis/openebs.io/v1alpha1/blockdeviceclaimbuilder.go

@@ -29,6 +29,10 @@ const (
 	StoragePoolKindCSPC = "CStorPoolCluster"
 	// APIVersion holds the value of OpenEBS version
 	APIVersion = "openebs.io/v1alpha1"
+
+	// bdTagKey defines the label selector key
+	// used for grouping block devices using a tag.
+	bdTagKey = "openebs.io/block-device-tag"
 )
 
 func NewBlockDeviceClaim() *BlockDeviceClaim {
@@ -144,6 +148,23 @@ func (bdc *BlockDeviceClaim) WithBlockVolumeMode(mode corev1.PersistentVolumeMod
 	return bdc
 }
 
+// WithBlockDeviceTag appends (or creates) the BDC Label Selector
+// by setting the provided value to the fixed key
+// openebs.io/block-device-tag
+// This will enable the NDM to pick only devices that
+// match the node (hostname) and block device tag value.
+func (bdc *BlockDeviceClaim) WithBlockDeviceTag(bdTagValue string) *BlockDeviceClaim  {
+	if bdc.Spec.Selector == nil {
+		bdc.Spec.Selector = &metav1.LabelSelector{}
+	}
+	if bdc.Spec.Selector.MatchLabels == nil {
+		bdc.Spec.Selector.MatchLabels = map[string]string{}
+	}
+
+	bdc.Spec.Selector.MatchLabels[bdTagKey] = bdTagValue
+	return bdc
+}
+
 // RemoveFinalizer removes the given finalizer from the object.
 func (bdc *BlockDeviceClaim) RemoveFinalizer(finalizer string) {
 	bdc.Finalizers = util.RemoveString(bdc.Finalizers, finalizer)