systemd-coredump.postinst: Create systemd-coredump system user

debian/changelog

@@ -8,6 +8,7 @@ systemd (229-1) UNRELEASED; urgency=medium
     - Do not warn about Wants depencencies on masked units. (LP: #1543282)
   * debian/systemd.install: Ship the new systemd-resolve.
   * libsystemd0.symbols: Add new symbols from this release.
+  * systemd-coredump.postinst: Create systemd-coredump system user.
   * debian/tests/systemd-fsckd: Tame overly strict test for failed plymouth
     unit, which is a race condition with plymouthd auto-stopping.
     (LP: #1543144)

debian/systemd-coredump.postinst

@@ -2,6 +2,9 @@
 set -e
 
 if [ "$1" = configure ]; then
+    adduser --quiet --system --group --no-create-home --home /run/systemd \
+        --gecos "systemd Time Synchronization" systemd-timesync
+
     # enable systemd-coredump right after package installation
     /lib/systemd/systemd-sysctl /usr/lib/sysctl.d/50-coredump.conf || true
 fi