public function getWellKnown()
    {
        $cached = $this->getCache('wellKnown');
        if (!empty($cached)) {
            return $cached;
        }

        try {
            $response = $this->client->get($this->wellKnownUrl);
        } catch (RequestException $e) {
            $this->lastException = $e;
            return null;
        }

        $output = json_decode($response->getBody());
        if (json_last_error() !== JSON_ERROR_NONE) {
            return null;
        }

        $this->setCache('wellKnown', $output);

        return $output;
    }