The Constrained Application Protocol (CoAP) is a specialized web
transfer protocol for use with constrained nodes and constrained
(e.g., low-power, lossy) networks.
This interface offers methods to control and communicate with instance of Device.
CoapController and Device should have one-to-one relationship, as class that implements
this interface is responsible for creating and adding CoapResource to instance of CoapServer.
Different Devices may offer access to different resources, therefore CoapController classes
should offer diversity to support this behavior.