@Override
        public HttpResponse serve(ServiceRequestContext ctx, HttpRequest req) throws Exception {
            return unwrap().serve(ctx, req).mapTrailers(trailers -> {
                final String extraHeader = req.headers().get(EXTRA_HEADER_NAME);
                if (extraHeader != null) {
                    return trailers.toBuilder().set(EXTRA_HEADER_NAME, extraHeader).build();
                }
                return trailers;
            });
        }
Creates a new instance that decorates the specified {@link Service}.
grpc/src/test/java/com/linecorp/armeria/internal/common/grpc/TestServiceImpl.java