code: function (backendSummary) {
          backendSummary = backendSummary || {};
  
          return {
              sum:            safeUse(backendSummary.subtotal),
              shipping:       safeUse(backendSummary.shipping),
              surcharge:      safeUse(backendSummary.surcharge),
              vat:            safeUse(backendSummary.vat),
              total:          safeUse(backendSummary.grandtotal)
          };
      }
docs: we want to make sure that the server returned summary can be used out of the box to work with our summary templates/directives, hence we have to convert it (similar to how we do it for the addresses).