text: app.service('TransactionService', ['$http', function($http) {
      return {
          add: function(products, successCallback) {
              $http.post('/api/transaction/', { products: JSON.stringify(products) }).then(successCallback);
          },
          extract: function(successCallback) {
              $http.get('/api/transaction/extract').then(successCallback);
          }
      };
  }]);
  