build: Remove cockpit(-ws-instance) user/group config option

[martinpitt]

All distributions use the same value anyway, and this paves the way for unifying them further with moving to systemd-sysusers.

We never test the upstream default of running them as root, so it might not even work and we also don't want to support/encourage that.

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Broken out of #20365 and fixed. I want to test/land this separately, as it's quite intrusive.

@travier FYI

The release note also covers the changes from #20425 and #20447.

webserver: System user changes

This release drops the ./configure options for customizing the two system users of cockpit's web server:
--with-cockpit-user, --with-cockpit-group, --with-cockpit-ws-instance-user, and --with-cockpit-ws-instance-user. All supported distributions use the same name anyway. We don't test, support, or recommend running the web server as root, which so far has been the default with ./configure; make; make install.

The cockpit-ws system user is not created statically at all, but created transiently and on demand via systemd's DynamicUser feature. If you want to, you can safely remove the static system user with e.g. userdel -r cockpit-ws after the upgrade to this version and after systemctl stop cockpit.

The cockpit-wsinstance system user is now declared through systemd-sysusers.

[mvollmer]

Initial reaction: Why not just change the defaults to cockpit-ws and cockpit-wsinstance and keep the configurability?

But then again it's nice to reduce complexity.

[martinpitt]

@mvollmer This was spawned from #20365 -- It's mostly cleaning up variability which we don't need anywhere or even test, and that autoconf seddery doesn't translate well into a world of "Linuxes should converge" and "use systemd sysusers everywhere". In particular, I'm not happy about defaulting "root". We could change the defaults, but it just feels like accidental complexity to me.

[allisonkarlitskaya]

Thanks for this very nice cleanup. I always thought we had to keep this because debian or something had historically different values. If they're all the same anyway, then ya, definitely burn it down!

[travier]

Thanks. Looks good.

[martinpitt]

@allisonkarlitskaya I updated the release note here to also contain the DynamicUser and sysuser changes.