Handle log rotation

As requested by @josegonzalez.

plugins/20_events/install

@@ -3,6 +3,9 @@ set -eo pipefail; [[ $DOKKU_TRACE ]] && set -x
 source "$(dirname $0)/../common/functions"
 
 DOKKU_RSYSLOG_FILTER=/etc/rsyslog.d/99-dokku.conf
+DOKKU_LOGROTATE_FILE=/etc/logrotate.d/dokku
+
+flag_rsyslog_needs_restart=n
 
 if [[ ! -f  "$DOKKU_EVENTS_LOGFILE" ]]; then
   touch "$DOKKU_EVENTS_LOGFILE"
@@ -15,6 +18,29 @@ if [[ ! -f  "$DOKKU_RSYSLOG_FILTER" ]]; then
   cat >"$DOKKU_RSYSLOG_FILTER" <<EOF
 :syslogtag, contains, "dokku" $DOKKU_EVENTS_LOGFILE
 EOF
+  flag_rsyslog_needs_restart=y
+fi
+
+if [[ ! -f "$DOKKU_LOGROTATE_FILE" ]]; then
+  cat >"$DOKKU_LOGROTATE_FILE" <<EOF
+$DOKKU_EVENTS_LOGFILE {
+        daily
+        rotate 7
+        missingok
+        notifempty
+        su syslog dokku
+        compress
+        delaycompress
+        postrotate
+                reload rsyslog >/dev/null 2>&1 || true
+        endscript
+        create 664 syslog dokku
+}
+EOF
+  flag_rsyslog_needs_restart=y
+fi
+
+if [[ "$flag_rsyslog_needs_restart" == "y" ]]; then
   service rsyslog restart
 fi