Add Google Cloud DNS plugin (#3011)

Signed-off-by: Palash Nigam <npalash25@gmail.com>

Closes: #2822

plugin/clouddns/gcp.go

@@ -0,0 +1,32 @@
+package clouddns
+
+import gcp "google.golang.org/api/dns/v1"
+
+type gcpDNS interface {
+	zoneExists(projectName, hostedZoneName string) error
+	listRRSets(projectName, hostedZoneName string) (*gcp.ResourceRecordSetsListResponse, error)
+}
+
+type gcpClient struct {
+	*gcp.Service
+}
+
+// zoneExists is a wrapper method around `gcp.Service.ManagedZones.Get`
+// it checks if the provided zone name for a given project exists.
+func (c gcpClient) zoneExists(projectName, hostedZoneName string) error {
+	_, err := c.ManagedZones.Get(projectName, hostedZoneName).Do()
+	if err != nil {
+		return err
+	}
+	return nil
+}
+
+// listRRSets is a wrapper method around `gcp.Service.ResourceRecordSets.List`
+// it fetches and returns the record sets for a hosted zone.
+func (c gcpClient) listRRSets(projectName, hostedZoneName string) (*gcp.ResourceRecordSetsListResponse, error) {
+	rr, err := c.ResourceRecordSets.List(projectName, hostedZoneName).Do()
+	if err != nil {
+		return nil, err
+	}
+	return rr, nil
+}