Polish up body-based routing server + add health check server

Author: rramkumar1

pkg/body-based-routing/handlers/request.go

@@ -59,7 +59,7 @@ func (s *Server) HandleRequestBody(body *eppb.HttpBody) (*eppb.ProcessingRespons
 						SetHeaders: []*basepb.HeaderValueOption{
 							{
 								Header: &basepb.HeaderValue{
-									Key:   "Model",
+									Key:   "model",
 									Value: modelStr,
 								},
 							},
@@ -87,4 +87,4 @@ func (s *Server) HandleRequestTrailers(trailers *eppb.HttpTrailers) (*eppb.Proce
 			RequestTrailers: &eppb.TrailersResponse{},
 		},
 	}, nil
-}
+}