Add unit tests for the authentication and authorization callbacks. Update README.md with the proposed callback configuration.
Make new CoAP unit tests pass

Add missing done calls to the new CoAP unit tests

Provide some examples for the CoAP authentication and authorization callbacks in the README.md
Make new HTTP unit tests pass

Update the configuration description of the authentication and authorization callbacks in the README.md
Correct the new unit tests of the MQTT server and make them pass