Upload VAT VIES example of interface-based injection

[lvanvugt]

In chapter 13 of my book I discuss how to test double calls to external services using as an example the VAT Registration number validation feature in standard BC. This calls upon the EU VAT registration validation service. The call has, however, been hard coded and as such is not easy to test double. In the book I show a possible approach making use of dependency injection (after having tweeked the standard code somewhat). In this example I do not yet make use of interface-based injection.
In this example however I do.