text: const mongoose = require('mongoose');
  const Schema = mongoose.Schema;
  const { ObjectId } = Schema.Types;
  
  const userstory_history = mongoose.Schema({    
      sprint_id: { type: ObjectId , ref: 'sprints'},
      attribute: { type: String, required: true },
      new_value: { type: String },
      old_value: { type: String },
      updated_by: { type: ObjectId, ref: 'users', required: true },
      timestamp: { type: String }
  },
      { strict: true });
  
  const userstory_history_Schema = mongoose.model('userstory_history', userstory_history);
  
  module.exports = { UserStoryHistory: userstory_history_Schema };