Prometheus - Donation and payment store

Changelog

1. Fixed an edge case where purchasing with credits would return a blank page if only credits is disabled and no custom price is set.
2. Fixed PHP warnings in phpfastcache and in the credits purchase flow.
3. Updated all our composer dependencies, this should fix some Stripe checkout errors.

Modified files

Web

1. vendor/*
2. inc/classes/coupon.class.php
3. inc/classes/packages.class.php
4. inc/credits.php
5. cache/drivers/files.php
6. cache/drivers/sqlite.php
7. cache/drivers/abstract.php
8. cache/drivers/phpfastcache.php