REST server endpoint compatible with ReqRes

The purpose of this task is to see the new Qt HTTP Server in action and provide a more complete example of using it for hosting RESTful services. The idea is to create an API-compatible implementation of https://reqres.in REST services for contacts which then can be used with the new and extended Address Book example. With this, the new Address Book example can work either directly with https://reqres.in or with the new service hosted via the Qt HTTP Server. Watch which code is required for the handling of REST and networking, and make observations on what part of this code will be repetitive in other user cases