protected function auth(): self 	{ 		if ($this->token) { 			return $this; 		}  		$data = $this->client->asForm()->withBasicAuth($this->clientId, $this->clientSecret)->post('v1/oauth2/token', ['grant_type' => 'client_credentials']); 		$data = $this->returnResponse($data);  		$this->token = $data['access_token'] ?? null;  		return $this; 	}