Add etcd basic auth support for coredns provider

docs/tutorials/coredns.md

@@ -87,6 +87,8 @@ helm install --name my-coredns --values values.yaml stable/coredns
 ### Install external ExternalDNS
 ETCD_URLS is configured to etcd client service address.
 
+If the etcd client being used has basic auth enabled, for example when using the [bitnami/etcd](https://artifacthub.io/packages/helm/bitnami/etcd) chart, the `ETCD_USERNAME` and `ETCD_PASSWORD` environment variables can be used to provide the credentials. 
+
 #### Manifest (for clusters without RBAC enabled)
 
 ```yaml

provider/coredns/coredns.go

@@ -205,8 +205,14 @@ func getETCDConfig() (*etcdcv3.Config, error) {
 	}
 	etcdURLs := strings.Split(etcdURLsStr, ",")
 	firstURL := strings.ToLower(etcdURLs[0])
+	etcdUsername := os.Getenv("ETCD_USERNAME")
+	etcdPassword := os.Getenv("ETCD_PASSWORD")
 	if strings.HasPrefix(firstURL, "http://") {
-		return &etcdcv3.Config{Endpoints: etcdURLs}, nil
+		return &etcdcv3.Config{
+			Endpoints: etcdURLs,
+			Username:  etcdUsername,
+			Password:  etcdPassword,
+		}, nil
 	} else if strings.HasPrefix(firstURL, "https://") {
 		caFile := os.Getenv("ETCD_CA_FILE")
 		certFile := os.Getenv("ETCD_CERT_FILE")
@@ -221,6 +227,8 @@ func getETCDConfig() (*etcdcv3.Config, error) {
 		return &etcdcv3.Config{
 			Endpoints: etcdURLs,
 			TLS:       tlsConfig,
+			Username:  etcdUsername,
+			Password:  etcdPassword,
 		}, nil
 	} else {
 		return nil, errors.New("etcd URLs must start with either http:// or https://")