add endpoints for comment of MessageSlice (#8805)
add endpoints for comment of MessageSlice (#8805)


smawson/istio,geeknoid/istio,istio/istio,smawson/istio,smawson/istio,istio/istio,smawson/istio,istio/istio,geeknoid/istio,istio/istio,geeknoid/istio,smawson/istio,smawson/istio,geeknoid/istio,istio/istio,geeknoid/istio,geeknoid/istio