Added support for group_add key

This PR will add support for `group_add` key which will map to
supplemental group in pod security context.

pkg/transformer/kubernetes/k8sutils.go

@@ -431,6 +431,11 @@ func (k *Kubernetes) UpdateKubernetesObjects(name string, service kobject.Servic
 			}
 		}
 
+		//set supplementalGroups
+		if service.GroupAdd != nil {
+			podSecurityContext.SupplementalGroups = service.GroupAdd
+		}
+
 		// Setup security context
 		securityContext := &api.SecurityContext{}
 		if service.Privileged {

pkg/transformer/kubernetes/kubernetes_test.go

@@ -55,6 +55,7 @@ func newServiceConfig() kobject.ServiceConfig {
 		TmpFs:         []string{"/tmp"},
 		Replicas:      2,
 		Volumes:       []kobject.Volumes{{SvcName: "app", MountPath: "/tmp/volume", PVCName: "app-claim0"}},
+		GroupAdd:      []int64{1003, 1005},
 	}
 }