test: add test case for issue user journal corruption

For issue systemd#24150 and systemd#31222.

test/test-functions

@@ -2099,7 +2099,7 @@ install_testuser() {
     # create unprivileged user for user manager tests
     mkdir -p "${initdir:?}/etc/sysusers.d"
     cat >"$initdir/etc/sysusers.d/testuser.conf" <<EOF
-u testuser    4711     "Test User" /home/testuser
+u testuser    4711     "Test User" /home/testuser /bin/bash
 EOF
 
     mkdir -p "$initdir/home/testuser"

test/units/testsuite-04.user-corrupt.sh

@@ -0,0 +1,22 @@
+#!/usr/bin/env bash
+# SPDX-License-Identifier: LGPL-2.1-or-later
+set -eux
+set -o pipefail
+
+journalctl --rotate --vacuum-files=1
+# Nuke all archived journals, so we start with a clean slate
+rm -f "/var/log/journal/$(</etc/machine-id)/system@*.journal"
+rm -f "/var/log/journal/$(</etc/machine-id)/user-*@*.journal"
+journalctl --header | grep path
+
+# Make sure the user instance is active when we rotate journals
+systemd-run --unit user-sleep.service --user -M testuser@ sleep infinity
+
+for _ in {0..10}; do
+    journalctl --rotate
+    journalctl --sync
+    SYSTEMD_LOG_LEVEL=debug journalctl -n1 -q
+    (! journalctl -n0 -q |& grep corrupted)
+done
+
+systemctl stop --user -M testuser@ user-sleep.service