Create a user.

        https://developers.meethue.com/documentation/configuration-api#71_create_user

async def create_user(self, device_type):
        """Create a user.

        https://developers.meethue.com/documentation/configuration-api#71_create_user
        """
        result = await self.request('post', '', {
            'devicetype': device_type
        }, auth=False)
        self.username = result[0]['success']['username']
        return self.username