Read Availability zone from nodeAffinity requirements

Velero to read the AZ info from `NodeAffinity` of a PV when it's taking
the snapshot.

Fixes #4332

Signed-off-by: Daniel Jiang <jiangd@vmware.com>

pkg/builder/node_selector_builder.go

@@ -0,0 +1,64 @@
+package builder
+
+import corev1api "k8s.io/api/core/v1"
+
+// NodeSelectorBuilder builds NodeSelector objects
+type NodeSelectorBuilder struct {
+	object *corev1api.NodeSelector
+}
+
+// ForNodeSelector returns the NodeSelectorBuilder instance with given terms
+func ForNodeSelector(term ...corev1api.NodeSelectorTerm) *NodeSelectorBuilder {
+	return &NodeSelectorBuilder{
+		object: &corev1api.NodeSelector{
+			NodeSelectorTerms: term,
+		},
+	}
+}
+
+// Result returns the built NodeSelector
+func (b *NodeSelectorBuilder) Result() *corev1api.NodeSelector {
+	return b.object
+}
+
+// NodeSelectorTermBuilder builds NodeSelectorTerm objects.
+type NodeSelectorTermBuilder struct {
+	object *corev1api.NodeSelectorTerm
+}
+
+// NewNodeSelectorTermBuilder initializes an instance of NodeSelectorTermBuilder
+func NewNodeSelectorTermBuilder() *NodeSelectorTermBuilder {
+	return &NodeSelectorTermBuilder{
+		object: &corev1api.NodeSelectorTerm{
+			MatchExpressions: make([]corev1api.NodeSelectorRequirement, 0),
+			MatchFields:      make([]corev1api.NodeSelectorRequirement, 0),
+		},
+	}
+}
+
+// WithMatchExpression appends the MatchExpression to the NodeSelectorTerm
+func (ntb *NodeSelectorTermBuilder) WithMatchExpression(key string, op string, values ...string) *NodeSelectorTermBuilder {
+	req := corev1api.NodeSelectorRequirement{
+		Key:      key,
+		Operator: corev1api.NodeSelectorOperator(op),
+		Values:   values,
+	}
+	ntb.object.MatchExpressions = append(ntb.object.MatchExpressions, req)
+	return ntb
+}
+
+// WithMatchField appends the MatchField to the NodeSelectorTerm
+func (ntb *NodeSelectorTermBuilder) WithMatchField(key string, op string, values ...string) *NodeSelectorTermBuilder {
+	req := corev1api.NodeSelectorRequirement{
+		Key:      key,
+		Operator: corev1api.NodeSelectorOperator(op),
+		Values:   values,
+	}
+	ntb.object.MatchFields = append(ntb.object.MatchFields, req)
+	return ntb
+}
+
+// Result returns the built NodeSelectorTerm
+func (ntb *NodeSelectorTermBuilder) Result() *corev1api.NodeSelectorTerm {
+	return ntb.object
+}