feat: multi-domain support

Description

Add multi-domain support to Grove. Users are now able to modify the GROVE_ADDITIONAL_DOMAINS settings to add extra domains to their LMS/CMS.

Supporting information

• https://tasks.opencraft.com/browse/SE-5877

Testing instructions

View the config for the instance at https://gitlab.com/opencraft/devstacks/keith/grove-do/-/blob/main/instances/es2/config.yml

These links point to the same LMS. Check that you're able to log in on both.

• https://es2.kgdocluster.opencraft.hosting/
• https://lms-es2.kgdocluster.opencraft.hosting/

Verify the SiteConfiguration that was generated is correct.

These point to the same CMS

• https://studio.es2.kgdocluster.opencraft.hosting/
• https://cms-es2.kgdocluster.opencraft.hosting/

Checklist

If any of the items below is not applicable, do not remove them, but put a check in it.

• Git commit history is clean
• Git commits are following conventional-commit practices
• Unit tests are added/updated
• Documentation is added/updated

Additional context

Add any other context about the merge request here.