> apt modernize-sources

What I lack with the "modern" `sources.list.d/` file schema is a command to perform common types of edits. Something like `extrepo` but generic and with knowledge of Debian repos/dists. It's a small thing but I want to be able to type commands like

    apt-sources available # prints known dists, marked by their support status
    apt-sources list         # prints all active dists
    apt-sources add trixie   # or "testing", "unstable", "sid"
    apt-sources remove bookworm
    apt-sources dist-upgrade # combo of the previous two

Perhaps `extrepo` would be extended to include Debian-proper or this hypothetical `apt-sources` would be kept Debian-repo-only or perhaps it would cover extrepo's scope.