def post(self):
        '''
        Adds a new user to the database.
        RESPONSE STATUS CODE:
         * Returns 201 if the user is created
         * Return 400 if the body is not well formed
         * Return 409 if invalid ID
         * Return 415 if unsupported media type
         * Return 500 if cannot access the database
        '''
        if JSON != request.headers.get('Content-Type',''):
            return create_error_response(415, "Unsupported Media Type",
                                         "Use a JSON compatible format")
        request_body = request.get_json(force=True)
        if not request_body:
            return create_error_response(415, "Unsupported Media Type",
                                         "Use a JSON compatible format",
                                         )

        data = request.data
        req = json.loads(data)
        nick = None
        email = None
        password =None

        for key in req.keys():
            if (key == "additionalName"):
                nick = req['additionalName']
            elif (key == "email"):
                email = req['email']
            elif (key == "password"):
                password = req['password']
        if (nick == None or email == None or password == None):
            return create_error_response(400, "Wrong request format",
                                         "Missing headline or user"
                                         )
        new_user = None
        try:
            new_user = g.con.add_user(nick, email, password, 1)
        except ValueError:
            return create_error_response(400, "Wrong request format",
                                         "Missing headline or user"
                                         )
        except sqlite3.IntegrityError:
            # Unexisting user
            return create_error_response(409, "Invalid used id. User doesn't exist",
                                         "Invalid user id"
                                         )

        if (new_user):
            return Response(
                status=201,
                headers={"Location": api.url_for(User,
                                                 user_id=new_user)})