implement grpc gateway and addl handler support

pkg/srv/grpc/prepare.go

@@ -50,6 +50,15 @@ func (a *appGRPCServer) prepGRPCServer(spanCtx context.Context) error {
 	a.registerGRPCServices(ctx)
 	span.SetAttributes(attribute.Int("grpc.server.grpcservices", len(a.opts.Services)))
 
+	// If a grpc-gateway mux was created, store it in opts
+	// so it can be used by AppHTTP
+	if a.gatewayMux != nil {
+		a.opts.SetGatewayMux(a.gatewayMux)
+		span.SetAttributes(attribute.Bool("grpc.server.grpcgateway.enabled", true))
+	} else {
+		span.SetAttributes(attribute.Bool("grpc.server.grpcgateway.enabled", false))
+	}
+
 	// Enable reflection if desired
 	if a.opts.EnableReflection {
 		reflection.Register(a.server)