text: const mongoose = require('mongoose');
  
  const Schema = mongoose.Schema;
  
  const bookSchema = new Schema({
      title:              {type: String, required: true },
      authors:            {type: String, required: false},
      editor:             {type: String, required: false},
      publicationDate:    {type: String, required: false},
      description:        {type: String, required: false},
      isbn:               {type: Number, required: false},
      quantity:           {type: Number, required: true },
      subtitle:           {type: String, required: false},
      urlImage:           {type: String, required: false}
  });
  
  module.exports = mongoose.model('Book', bookSchema);