Add machine readable Debian copyright file

Per https://www.debian.org/doc/packaging-manuals/copyright-format/1.0/

debian/copyright

@@ -1,28 +1,8 @@
-
-libpam-tacplus
-
-    Copyright (C) 2010, Pawel Krawczyk <pawel.krawczyk@hush.com>
-    and Jeroen Nijhof <jeroen@jeroennijhof.nl>.
-
-    This program is free software; you can redistribute it and/or modify
-    it under the terms of the GNU General Public License as published by
-    the Free Software Foundation; either version 2 of the License, or
-    (at your option) any later version.
-
-    This program is distributed in the hope that it will be useful,
-    but WITHOUT ANY WARRANTY; without even the implied warranty of
-    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-    GNU General Public License for more details.
-
-    You should have received a copy of the GNU General Public License
-    along with this program; if not, write to the Free Software
-    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston,
-    MA 02110-1301, USA.
-
-All the other scripts and control files for building and installing
-libpam-tacplus under Debian GNU/Linux are also under the GNU General Public
-License (GPL) version 2 or later.
-
-On Debian GNU/Linux systems, the complete text of the GNU General
-Public License can be found in '/usr/share/common-licenses/GPL-2'.
-
+Format: https://www.debian.org/doc/packaging-manuals/copyright-format/1.0/
+Upstream-Contact: Pawel Krawczyk <p+debian@krvtz.net>
+Source: https://github.com/kravietz/pam_tacplus
+Upstream-Name: pam_tacplus
+
+Files: *
+Copyright: 2022 Pawel Krawczyk, Jeroen Nijhof
+License: GPL-3+