Google_Service_Groupssettings_Resource_Groups::get returns object with all properties null

[legendhb]

Environment details

• PHP version: 7.3
• Package name and version: "google/apiclient": "^2.11"

Steps to reproduce

1. try to retrieve Group Settings via PHP SDK.

Code example

$settings = (new \Google_Service_Groupssettings($this->getClient()))->groups->get('[email protected]');
var_dump($settings);    // Object Google\Service\Groupssettings\Groups with all properties null.

I've tried to trace the code, body of HTTP response was XML, bug SDK tries to parse the body with json_decode(). Add optParams to specify response format to JSON could solve this problem,

$settings = (new \Google_Service_Groupssettings($this->getClient()))->groups->get('[email protected]', ['alt' => 'json']);
var_dump($settings);    // seems ok

It's better for SDK to add this optParams automatically, instead of letting developer to add this param manually.

Thanks!