old_contents: var mongoose = require('mongoose');
  var Schema = mongoose.Schema;
  var mongooseUniqueValidator = require('mongoose-unique-validator');
  
  var bookmarkSchema = new Schema({
      name: {type:String, required: true, unique: true},
      url: {type:String, required: true, unique: true},
      description: String,
      category: {type:String, required: true},
      tags: [String]
  },
  {
    timestamps: true
  });
  
  bookmarkSchema.plugin(mongooseUniqueValidator);
  
  module.exports = mongoose.model('Bookmark', bookmarkSchema);
  
new_contents: var mongoose = require('mongoose');
  var Schema = mongoose.Schema;
  var mongooseUniqueValidator = require('mongoose-unique-validator');
  
  var bookmarkSchema = new Schema({
      name: {type:String, required: true, unique: true},
      location: {type:String, required: true, unique: true},
      description: String,
      category: {type:String, required: true},
      tags: [String]
  },
  {
    timestamps: true
  });
  
  bookmarkSchema.plugin(mongooseUniqueValidator);
  
  module.exports = mongoose.model('Bookmark', bookmarkSchema);
  
subject: rename url attribute to location