fix(script): Add event allow-list

notify_signal_about_traccar_events.sh.conf.example

@@ -1,3 +1,22 @@
+# List of events on which this script will act. This is a Posix Extended
+# Regular Expression (ERE). Most Perl-Compatible Regular Expression
+# (PCRE) syntax works. Most notably lookarounds are unsupported in ERE.
+# Default's '^(deviceOnline|deviceUnknown|geofenceEnter|geofenceExit)$'.
+# Any event not in this list will be discarded. Note that this script
+# only /gracefully/ acts on these four events anyway. You can have it
+# act on any other event as well but in its current state that just
+# triggers the message_event_other Signal message which is decidedly
+# /ungraceful/, its usefulness is limited.
+#
+# For a list of events refer to github.com/traccar/traccar, specifically
+# the 'src/main/java/org/traccar/model/Event.java' file that lists all
+# available event names.
+allow_list_events='^(deviceOnline|deviceUnknown|geofenceEnter|geofenceExit)$'
+
+# If an event comes in that's not in allow_list_events we print this
+# message to stdout and exit.
+message_event_type_not_allowed='Event "%s" not allowed. Nothing to do.\n'
+
 # First positional argument '%s' is Traccar device name, second
 # positional argument '%s' is geofence name, third one is battery level.
 # This cannot be switched around, please word your message accordingly.
@@ -8,7 +27,6 @@ message_geofence_exit='%s left geofence %s.\\n\\nBattery level %s%%.'
 # Argument '%s' is Traccar device name
 message_device_online='On %s Traccar Client app is now active.'
 message_device_unknown='On %s Traccar Client app has not checked in for 10 minutes, the app is likely off now.'
-message_device_offline='On %s Traccar Client app is now off.'
 
 # Argument '%s' is Traccar device name but this one unlike the three
 # message strings before is used as stdout log output when the device ID