BeforeBasketPayments
This event will be fired right before getting the list with available payments for specific basket.
BeforeBasketPaymentsEventSubscriber
<?php
declare(strict_types=1);
namespace Full\Qualified\Namespace;
use OxidEsales\EshopCommunity\Internal\Framework\Event\AbstractShopAwareEventSubscriber;
use OxidEsales\GraphQL\Storefront\Basket\Event\BeforeBasketPayments;
class DeveloperBeforeBasketPaymentsEventSubscriber extends AbstractShopAwareEventSubscriber
{
    public function handle(BeforeBasketPayments $event): BeforeBasketPayments
    {
        //get the user basket id from event
        $userBasketId = (string) $event->getBasketId();
        //do something
        return $event;
    }
    public static function getSubscribedEvents()
    {
        return [
            'OxidEsales\GraphQL\Storefront\Basket\Event\BeforeBasketPayments' => 'handle'
        ];
    }
}
Important
The code above is only an example. In case you need to handle the BeforeBasketPayments event,
please adapt to your needs.
services.yaml
services:
    _defaults:
        public: false
        autowire: true
    Full\Qualified\Namespace\DeveloperBeforeBasketPaymentsEventSubscriber:
        class: Full\Qualified\Namespace\DeveloperBeforeBasketPaymentsEventSubscriber
        tags: ['kernel.event_subscriber']