shell: define three system credentials we can propagate into shell prompts and welcome messages

tmpfiles.d/20-systemd-shell-extra.conf.in

@@ -0,0 +1,12 @@
+#  This file is part of systemd.
+#
+#  systemd is free software; you can redistribute it and/or modify it
+#  under the terms of the GNU Lesser General Public License as published by
+#  the Free Software Foundation; either version 2.1 of the License, or
+#  (at your option) any later version.
+
+# See tmpfiles.d(5) for details
+
+{% if LINK_SHELL_EXTRA_DROPIN %}
+L {{SHELLPROFILEDIR}}/70-systemd-shell-extra.sh - - - - {{LIBEXECDIR}}/profile.d/70-systemd-shell-extra.sh
+{% endif %}

tmpfiles.d/meson.build

@@ -36,6 +36,7 @@ in_files = [['etc.conf',                      ''],
             ['var.conf',                      ''],
             ['20-systemd-userdb.conf',        'ENABLE_SSH_USERDB_CONFIG'],
             ['20-systemd-ssh-generator.conf', 'ENABLE_SSH_PROXY_CONFIG'],
+            ['20-systemd-shell-extra.conf',   'LINK_SHELL_EXTRA_DROPIN'],
            ]
 
 foreach pair : in_files