[Bug]: config.default_locale / CONFIG_DEFAULT_LOCALE does not change the default locale of the site

[tbiering]

Description

Setting the value of config.default_locale / CONFIG_DEFAULT_LOCALE does not change the behaviour of the app when visiting as an unregistered user. The site is always displayed in english locale.
This has been tested with a dockerized installation and setting the environment variable CONFIG_DEFAULT_LOCALE to any locale value currently available.

Describe the solution you'd like

Setting the configuration value should set the default locale for any unregistered user visiting the site.

Describe alternatives you've considered

I have prepared a pull request with a fix that I will link after creating the issue-ticket.