Add logrotate config for pmgproxy.log

to keep the log from growing without end. Rotate monthly and keep 12 logs,
since the logs should not be too large (e.g. a productive instance, with
~20 users using the quarantine and some configuration changes amounts to
108M over 2.5 years)

the logrotate snippet is placed in /etc/logrotate.d/pmg-api by
dh_installlogrotate(1).

Signed-off-by: Stoiko Ivanov <s.ivanov@proxmox.com>

debian/pmg-api.logrotate

@@ -0,0 +1,13 @@
+/var/log/pmgproxy/pmgproxy.log {
+	rotate 12
+	monthly
+	missingok
+	compress
+	delaycompress
+	notifempty
+	create 640 www-data www-data
+	sharedscripts
+	postrotate
+		/bin/systemctl try-reload-or-restart pmgproxy.service
+	endscript
+}