The Client.php constructor is problematic as it doesn't allow (e.g.) the TLS cert path to be set in an extension.

[geoidesic]

See inline comments about Client.php

    public function __construct($config)
    {
        $this->validate_config($config);   //<-- this is private, so I can't fully override this method

        $access_token = $config['access_token'];

        if (isset($config['base_url'])) {
            $endpoint_url = $config['base_url'];
        } else if (isset($config['environment'])) {
            $endpoint_url = $this->getUrlForEnvironment($config['environment']);  //<--  this is also private
        } else {
            throw new \InvalidArgumentException("Please specify an environment");
        }

        if (isset($config['http_client'])) {
            $http_client = $config['http_client'];
        } else {
            $stack = \GuzzleHttp\HandlerStack::create();
            $stack->push(RetryMiddlewareFactory::buildMiddleware());

            $timeout = 0;
            if(isset($config['timeout'])) {
                $timeout = $config['timeout'];
            }

            $http_client = new \GuzzleHttp\Client(
                [
                'base_uri' => $endpoint_url,
                'timeout' => $timeout,
                'headers' => array(
                'GoCardless-Version' => '2015-07-06',
                'Accept' => 'application/json',
                'Content-Type' => 'application/json',
                'Authorization' => "Bearer " . $access_token,
                'GoCardless-Client-Library' => 'gocardless-pro-php',
                'GoCardless-Client-Version' => '4.28.0',
                'User-Agent' => $this->getUserAgent()
                ),
                'http_errors' => false,
                'verify' => true,                        //<--  this is hard-coded, there's no way to edit this value.
                'handler' => $stack
                ]
            );
        }
        $this->api_client = new \GoCardlessPro\Core\ApiClient($http_client, $config);
    }

    ```
    
The reason I would like to be able to set the `verify` property of the `$http_client` is because of this error when trying to use GoCardless via Guzzle:
    

Deprecated: Creation of dynamic property GoCardlessPro\Core\ApiClient::$http_client is deprecated in /var/www/html/SportchLegacyApp/support/vendor/gocardless/gocardless-pro/lib/Core/ApiClient.php on line 24

Deprecated: Creation of dynamic property GoCardlessPro\Core\ApiClient::$error_on_idempotency_conflict is deprecated in /var/www/html/SportchLegacyApp/support/vendor/gocardless/gocardless-pro/lib/Core/ApiClient.php on line 25

Deprecated: Creation of dynamic property GoCardlessBridge::$redirect_flows is deprecated in /var/www/html/SportchLegacyApp/support/vendor/gocardless/gocardless-pro/lib/Client.php on line 404

Fatal error: Uncaught GuzzleHttp\Exception\RequestException: cURL error 60: SSL certificate problem: unable to get local issuer certificate (see https://curl.haxx.se/libcurl/c/libcurl-errors.html) for https://api-sandbox.gocardless.com/redirect_flows in