text: const mongoose = require('mongoose');
  
  const Purchase = new mongoose.Schema({
    ad: {
      type: mongoose.Schema.Types.ObjectId,
      ref: 'Ad',
      required: true,
    },
    content: {
      type: String,
      required: true,
    },
    user: {
      type: mongoose.Schema.Types.ObjectId,
      ref: 'User',
      required: true,
    },
    createdAt: {
      type: Date,
      default: Date.now,
    },
  });
  
  module.exports = mongoose.model('Purchase', Purchase);
  