Functional requirements:

The shopping cart overview service is responsible for:
* Calculation the final price a customer has to pay based on:
  ** Product and their product specific price reductions. These are provided by the calling application.
  ** Customer specific price reductions.
  ** Calculating the shipping cost.
* Adding specific customer type free products
   ** eco : get a free bag of compost
   ** nagging : get free self help book
   ** vip : get a gold plated lighter