Support binding gRPC services that are defined as object literals.

This commit allows binding gRPC services directly, in the following way:

const greeter = {
  greet: (req) => TestResponse.create({ greeting: `Hello` })
};

src/server/base_restate_server.ts

@@ -221,6 +221,22 @@ export abstract class BaseRestateServer {
   }
 }
 
+/* eslint-disable @typescript-eslint/no-explicit-any */
+function indexProperties(instance: any): Map<string, string> {
+  const names = new Map<string, string>();
+  while (
+    instance !== null &&
+    instance !== undefined &&
+    instance !== Object.prototype
+  ) {
+    for (const property of Object.getOwnPropertyNames(instance)) {
+      names.set(property.toLowerCase(), property);
+    }
+    instance = Object.getPrototypeOf(instance);
+  }
+  return names;
+}
+
 // Given:
 // * an instance of a class that implements a gRPC TypeScript interface,
 //   as generated by our protoc plugin, this method
@@ -263,14 +279,7 @@ export function parseService(
 
   // index all the existing properties that `instance` has.
   // we index them by the lower case represention.
-  const prototype = Object.getPrototypeOf(instance);
-  const names = new Map<string, string>(
-    Object.getOwnPropertyNames(prototype).map((name) => [
-      name.toLowerCase(),
-      name,
-    ])
-  );
-
+  const names = indexProperties(instance);
   for (const serviceDescriptor of meta.fileDescriptor.service) {
     if (serviceName !== serviceDescriptor.name) {
       continue;

test/service_bind.test.ts

@@ -0,0 +1,37 @@
+/*
+ * Copyright (c) 2023 - Restate Software, Inc., Restate GmbH
+ *
+ * This file is part of the Restate SDK for Node.js/TypeScript,
+ * which is released under the MIT license.
+ *
+ * You can find a copy of the license in file LICENSE in the root
+ * directory of this repository or package, or at
+ * https://github.com/restatedev/sdk-typescript/blob/main/LICENSE
+ */
+
+import {
+  TestGreeter,
+  TestRequest,
+  TestResponse,
+} from "../src/generated/proto/test";
+import * as restate from "../src/public_api";
+import { describe } from "@jest/globals";
+import { TestDriver } from "./testdriver";
+import { greetRequest, inputMessage, startMessage } from "./protoutils";
+
+const greeter: TestGreeter = {
+  /* eslint-disable @typescript-eslint/no-unused-vars */
+  greet: async (req: TestRequest): Promise<TestResponse> => {
+    restate.useContext(this);
+    return TestResponse.create({ greeting: `Hello` });
+  },
+};
+
+describe("BindService", () => {
+  it("should bind object literals", async () => {
+    await new TestDriver(greeter, [
+      startMessage(1),
+      inputMessage(greetRequest("Pete")),
+    ]).run();
+  });
+});