text: const mongoose = require('mongoose');
  const Schema = mongoose.Schema;
  
  const NotificationSchema = new Schema({
    owner: {
      type: Schema.Types.ObjectId,
      ref: 'User',
      required: true,
    },
    guest: {
      type: Schema.Types.ObjectId,
      ref: 'User',
      required: true,
    },
    book: {
      type: Schema.Types.ObjectId,
      ref: 'Book',
      required: true,
    },
    type: {
      type: String,
      enum: ['request', 'accept', 'done'],
      required: true,
    },
    isRead: {
      type: Boolean,
      default: false,
    },
    createAt: {
      type: Date,
      default: Date.now,
    },
  });
  
  module.exports = mongoose.model('Notification', NotificationSchema);
  