Add WorkingDirectory to systemd sample config.
Otherwise `initdb` fails because it tries to create the data directory in the root directory where the postgres user has no permissions.
@@ -11,6 +11,8 @@ Type=simple
User=postgres
Group=postgres
+WorkingDirectory=~
+
# Where to send early-startup messages from the server
# This is normally controlled by the global default set by systemd
# StandardOutput=syslog
