Store sessions in database instead of files

[frank9999]

Symfony stores sessions in files by default. If your application is served by multiple servers, you'll need to use a database instead to make sessions work across different servers.

At random times we also experience the following error:
Notice: SessionHandler::gc(): ps_files_cleanup_dir: opendir(/var/lib/php/sessions) failed: Permission denied (13)

Replacing file based sessions with database sessions should fix both cases.

How to:
https://symfony.com/doc/current/session.html#store-sessions-in-a-relational-database-mariadb-mysql-postgresql