Create a /credential-manifest endpoint to accept new Credential Manifests

Needs to look somthing like this:

import { DWN } from "@TBD54566975/dwn-sdk-js";

console.log(`Setting up routes...`);
const router = new Router();
router.post("/credential-manifest", async (res, _next) => {

// create dwn message from our cm json object
let dnwMessage = manifestJsonToDwnMessage(res.body);

// process dwn message
const response = await dwn.processRequest({ messages: [dnwMessage]} as any);
setKoaResponse(response, ctx.response);
});