* DEV: Skip push notifications for active online users
Currently, users with active push subscriptions get push notifications
regardless of their "presence" on the site.
This change introduces a `push_notification_time_window_mins`
site setting which is used in conjunction with a user's `last_seen_at` to
determine if push notifications should be sent. A user is considered to
be actively online if their `last_seen_at` is within `push_notification_time_window_mins`
minutes. `push_notification_time_window_mins` is set to 10 by default.
* DEV: Remove client param for push_notification_time_window_mins site setting
Co-authored-by: Bianca Nenciu <nbianca@users.noreply.github.com>
Co-authored-by: Bianca Nenciu <nbianca@users.noreply.github.com>
