document API guarentees and deprecation policies for cloud config files

Signed-off-by: Andrew Sy Kim <kiman@vmware.com>

pkg/cloudprovider/providers/openstack/openstack.go

@@ -146,6 +146,11 @@ type OpenStack struct {
 }
 
 // Config is used to read and store information from the cloud configuration file
+// NOTE: Cloud config files should follow the same Kubernetes deprecation policy as
+// flags or CLIs. Config fields should not change behavior in incompatible ways and
+// should be deprecated for at least 2 release prior to removing.
+// See https://kubernetes.io/docs/reference/using-api/deprecation-policy/#deprecating-a-flag-or-cli
+// for more details.
 type Config struct {
 	Global struct {
 		AuthURL         string `gcfg:"auth-url"`