如何在mongoose中组合两个模型属性生成唯一键哈希

const mongoose = require('mongoose');
const crypto = require('crypto');

// 创建User模型
const userSchema = new mongoose.Schema({
  email: {
    type: String,
    required: true
  },
  // 其他属性...
});

const User = mongoose.model('User', userSchema);

// 创建Product模型
const productSchema = new mongoose.Schema({
  name: {
    type: String,
    required: true
  },
  // 其他属性...
});

const Product = mongoose.model('Product', productSchema);

productSchema.virtual('uniqueKey').get(function () {
  const email = this.user.email; // 假设Product模型有一个user属性，关联到User模型
  const name = this.name;
  const hash = crypto.createHash('md5').update(email + name).digest('hex');
  return hash;
});

productSchema.pre('save', async function (next) {
  const product = await Product.findOne({ uniqueKey: this.uniqueKey });
  if (product) {
    const error = new Error('Duplicate unique key');
    // 处理错误...
    next(error);
  } else {
    next();
  }
});