Add patroni_use_kubernetes parameter.

Add a dedicated parameter to enable support for Kubernetes in Patroni
instead of relying on a legacy hack of setting etcd_host to an empty
string. The latter still works, however, it will show a warning, nudging
users to change to the new parameter.

For the sake of not breaking existing non-Kubernetes setups,
patroni_use_kubernetes has not effect if etcd_host is set to a non-empty
value.

pkg/cluster/cluster.go

@@ -927,7 +927,7 @@ type ClusterObjectDelete func(name string) error
 
 func (c *Cluster) deletePatroniClusterObjects() error {
 	// TODO: figure out how to remove leftover patroni objects in other cases
-	if !c.patroniUsesKubernetes() {
+	if !c.OpConfig.PatroniUseKubernetes {
 		c.logger.Infof("not cleaning up Etcd Patroni objects on cluster delete")
 	}
 	c.logger.Debugf("removing leftover Patroni objects (endpoints or configmaps)")

pkg/cluster/k8sres.go

@@ -399,7 +399,7 @@ func (c *Cluster) generatePodTemplate(
 		envVars = append(envVars, v1.EnvVar{Name: "LOG_BUCKET_SCOPE_PREFIX", Value: ""})
 	}
 
-	if c.patroniUsesKubernetes() {
+	if c.OpConfig.PatroniUseKubernetes {
 		envVars = append(envVars, v1.EnvVar{Name: "DCS_ENABLE_KUBERNETES_API", Value: "true"})
 	} else {
 		envVars = append(envVars, v1.EnvVar{Name: "ETCD_HOST", Value: c.OpConfig.EtcdHost})

pkg/cluster/util.go

@@ -460,7 +460,3 @@ func (c *Cluster) GetSpec() (*spec.Postgresql, error) {
 	defer c.specMu.RUnlock()
 	return cloneSpec(&c.Postgresql)
 }
-
-func (c *Cluster) patroniUsesKubernetes() bool {
-	return c.OpConfig.EtcdHost == ""
-}