Implement filtering of desktop notifications

Fixes #7670

docs/notifications.py

@@ -0,0 +1,49 @@
+#!/usr/bin/env python
+
+# A sample script to process notifications. Save it as
+# ~/.config/kitty/notifications.py
+
+import subprocess
+
+from kitty.notifications import NotificationCommand, Urgency
+
+
+def log_notification(nc: NotificationCommand) -> None:
+    # Log notifications to /tmp/notifications-log.txt
+    with open('/tmp/notifications-log.txt', 'a') as log:
+        print(f'title: {nc.title}', file=log)
+        print(f'body: {nc.body}', file=log)
+        print(f'app: {nc.application_name}', file=log)
+        print(f'type: {nc.notification_type}', file=log)
+        print('\n', file=log)
+
+
+def main(nc: NotificationCommand) -> bool:
+    '''
+    This function should return True to filter out the notification
+    '''
+    log_notification(nc)
+
+    # filter out notifications with 'unwanted' in their titles
+    if 'unwanted' in nc.title.lower():
+        return True
+
+    # filter out notifications from the application badapp
+    if nc.application_name == 'badapp':
+        return True
+
+    # filter out low urgency notifications
+    if nc.urgency is Urgency.Low:
+        return True
+
+    # replace some bad text in the notification body
+    nc.body = nc.body.replace('bad text', 'good text')
+
+    # run a script if this notification is from myapp and has
+    # type foo, passing in the title and body as command line args
+    # to the script.
+    if nc.application_name == 'myapp' and nc.notification_type == 'foo':
+        subprocess.Popen(['/path/to/my/script', nc.title, nc.body])
+
+    # dont filter out this notification
+    return False