VOL-3616 Support for API to retrieve information (example UNI) from an ONU
This commit implements extension service, which includes handling of the GetExtValue and SetExtValue APIs

Change-Id: I537160af5b70eccef77a8bc11235af3b50f9a513
diff --git a/vendor/modules.txt b/vendor/modules.txt
index b190e83..649a9c3 100644
--- a/vendor/modules.txt
+++ b/vendor/modules.txt
@@ -120,6 +120,7 @@
 # github.com/opencord/voltha-protos/v4 v4.0.5
 github.com/opencord/voltha-protos/v4/go/common
 github.com/opencord/voltha-protos/v4/go/ext/config
+github.com/opencord/voltha-protos/v4/go/extension
 github.com/opencord/voltha-protos/v4/go/inter_container
 github.com/opencord/voltha-protos/v4/go/omci
 github.com/opencord/voltha-protos/v4/go/openflow_13