API 接口对接流程：先核对认证、请求、响应和错误格式

import http from 'node:http';
import { randomUUID } from 'node:crypto';
const records = new Map();
const server = http.createServer(async (req, res) => {
  const send = (status, body) => {
    res.writeHead(status, {'content-type':'application/json', 'x-request-id':randomUUID()});
    res.end(JSON.stringify(body));
  };
  if (req.method !== 'POST' || req.url !== '/v1/orders') return send(404, {error:'route_not_found'});
  if (req.headers.authorization !== 'Bearer lesson') return send(401, {error:'unauthorized'});
  const key = req.headers['idempotency-key'];
  if (!key) return send(400, {error:'missing_idempotency_key'});
  let body;
  try { let text = ''; for await (const part of req) text += part; body = JSON.parse(text); }
  catch { return send(400, {error:'invalid_json'}); }
  if (!body || typeof body.sku !== 'string' || !body.sku.trim() || !Number.isInteger(body.quantity) || body.quantity < 1)
    return send(422, {error:'invalid_order'});
  const fingerprint = JSON.stringify({sku:body.sku, quantity:body.quantity});
  const previous = records.get(key);
  if (previous) return previous.fingerprint === fingerprint
    ? send(200, previous.order) : send(409, {error:'idempotency_conflict'});
  const order = {id:randomUUID(), sku:body.sku, quantity:body.quantity};
  records.set(key, {fingerprint, order}); send(201, order);
});
server.listen(3210, '127.0.0.1', () => console.log('POST http://127.0.0.1:3210/v1/orders'));

$headers = @{ Authorization = 'Bearer lesson'; 'Idempotency-Key' = 'lesson-order-1' }
$body = @{ sku = 'A-17'; quantity = 2 } | ConvertTo-Json -Compress
$response = Invoke-WebRequest -Uri 'http://127.0.0.1:3210/v1/orders' -Method Post -Headers $headers -ContentType 'application/json' -Body $body -SkipHttpErrorCheck
$response.StatusCode
$response.Headers['x-request-id']
$response.Content
# 原样再次执行 Invoke-WebRequest：预期200，订单id不变。
# 使用同一键，把quantity改为3：预期409。
# 删除Authorization：预期401；新键且quantity=0：预期422。