How to add custom action button in the SiteConfig extension

Silverstripe Version: 4.3.0

Question: How to add custom action button in the SiteConfig extension

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Trying to add a button under settings which calls an API and updated the database on click. I’ve extended Silverstripe\SiteConfig\SiteConfig and added the button

$fields->addFieldToTab('Root.WebsiteSettings.Shop', FormAction::create('syncShopProducts', 'Sync shop product')->addExtraClass('btn action btn-primary'));

How do I add the controller? or the function syncShopProducts