Fix background image selection
The first commit fixes storing the background image in AccountsService and retrieving a default from GSettings. The rest are various build fixes.
The 17.0 major release is coming on May 16, 2024! This version brings many exciting improvements to GitLab, but also removes some deprecated features. We are introducing three breaking change windows during which we expect breaking changes to be deployed to GitLab.com. You can read more about it on our blogpost. The second breaking change window begins 2024-04-29 09:00 UTC and ends 2024-05-01 22:00 UTC.
The first commit fixes storing the background image in AccountsService and retrieving a default from GSettings. The rest are various build fixes.