text: const gstore = require('gstore-node')();
  
  const { Schema } = gstore;
  
  /**
   * Create the schema for the User Model
  */
  const authenticationSchema = new Schema({
      id: { type: String, required: true },
      access_token: { type: String, required: true  },
      token_refresh_interval_sec: { optional: true },
      created_on: { type: String, default: gstore.defaultValues.NOW, write: false, read: true },
  });
  
  /**
   * List entities query shortcut
   */
  const listSettings = {
      limit: 15,
      order: { property: 'lastname' }
  };
  authenticationSchema.queries('list', listSettings);
  
  /**
   * Export the User Model
   * It will generate "User" entity kind in the Datastore
  */
  module.exports = gstore.model('authentication', authenticationSchema);
  