Web exercises backend

This backend can be used for the web exercises in the IIoT course.

It provides a simple calculator website which can be requested using a HTTP POST request.

It provides a simple greet REST API, OpenAPI documentation is here.

Finally, it runs 2 Web Socket based services: A simple chat on ws://webex.iiot.synd.hevs.ch/chat and
a simulated temperature and battery sensor on ws://webex.iiot.synd.hevs.ch/temp.
Both services are available as a secure variant too:
wss://webex.iiot.synd.hevs.ch/chat and wss://webex.iiot.synd.hevs.ch/temp.