old_contents: 'use strict';
  
  /**
   * @param {import('../models').Playlist} model
   */
  function serializePlaylist(model) {
    return {
      _id: model.id || model._id.toString(),
      name: model.name,
      author: model.author,
      createdAt: model.createdAt,
      description: model.description,
      size: model.media.length,
    };
  }
  
  /**
   * @param {Pick<import('../models').User,
   *   '_id' | 'username' | 'slug' | 'roles' | 'avatar' |
   *   'createdAt' | 'updatedAt' | 'lastSeenAt'>} model
   */
  function serializeUser(model) {
    return {
      _id: model._id.toString(),
      username: model.username,
      slug: model.slug,
      roles: model.roles,
      avatar: model.avatar,
      createdAt: model.createdAt.toString(),
      updatedAt: model.updatedAt.toString(),
      lastSeenAt: model.lastSeenAt.toString(),
    };
  }
  
  exports.serializePlaylist = serializePlaylist;
  exports.serializeUser = serializeUser;
  
new_contents: 'use strict';
  
  /**
   * @param {import('../models').Playlist} model
   */
  function serializePlaylist(model) {
    return {
      _id: model.id || model._id.toString(),
      name: model.name,
      author: model.author.toString(),
      createdAt: model.createdAt.toISOString(),
      description: model.description,
      size: model.media.length,
    };
  }
  
  /**
   * @param {Pick<import('../models').User,
   *   '_id' | 'username' | 'slug' | 'roles' | 'avatar' |
   *   'createdAt' | 'updatedAt' | 'lastSeenAt'>} model
   */
  function serializeUser(model) {
    return {
      _id: model._id.toString(),
      username: model.username,
      slug: model.slug,
      roles: model.roles,
      avatar: model.avatar,
      createdAt: model.createdAt.toISOString(),
      updatedAt: model.updatedAt.toISOString(),
      lastSeenAt: model.lastSeenAt.toISOString(),
    };
  }
  
  exports.serializePlaylist = serializePlaylist;
  exports.serializeUser = serializeUser;
  
subject: Fix serialization of Dates in user and playlist objects