Code review comment for ~litios/ubuntu-security-tools:build-sources-list/use-auth-conf

Hey Alex, thanks for the review!

I refactored it to be a new file and added an echo statement in the original file for people to know they should run it too to get the credentials.

Regarding the permission issue, having the group as sudo for the file should allow the main user and any other user in the sudo group to be able to read the file. It's the same as we are doing for the files in sources.list.d too. https://pastebin.canonical.com/p/3CXGFDPzqV/.

It makes it work for umt while not setting world-read permission. But let me know if you find an issue with this and I can revert it to world-read.