PCP-299: Add binding to pp-issuer using handlers

[lbaquerofierro]

Use RCP-fetch, pp-proxy caller would look something like:

export default {
  async fetch(request: Request, env: Bindings, ctx: ExecutionContext) {
    const router = new Router(VALID_PATHS);

    router
      .get("/.well-known/private-token-issuer-directory", testRCPBinding);

    // Await the response
    let res = await router.handle(
      request as Request<Bindings, IncomingRequestCfProperties<unknown>>,
      env,
      ctx
    );

    return res;
  },
};

async function testRCPBinding(context: Context, request: Request): Promise<Response> {
  const res = await context.env.PRIVACYPASS_ISSUER.tokenDirectory(request, "US-PST");
  const headers = res.responseHeaders;
  const body = JSON.stringify(res.responseBody);
  return new Response(body, { headers });
}

pp-issuer wrangler

[[env.dev.services]]
binding = "PRIVACYPASS_ISSUER"
service = "privacypass-issuer-demo-dev" # change to new mallard issuer
entrypoint = "IssuerHandler"

Note PRIVACYPASS_ISSUER and IssuerHandler are defined in pp-issuer. We can either duplicate the code to define it or add the service as a binding in pp proxy and define the type for IssuerHandler which is basically all the handler functions in pp-issuer