Error messages have now formalized output in JSON which includes both message and error code. Status of the response is also set accordingly. There is still few bugs in the system which might invoke Django's
own error responses (for example trying to create objects with same uuid, or having scandinavian characters in the url for PUT. Next I'm trying to iron out these minor problems, thought without automated/professional testing there might still remain
similar problems.

Success messages have also been fine-tuned a bit to be in proper JSON format.