Django implementations for VintaSend.
DjangoDbNotificationBackend implements the full notification backend, including the in-app
listing API: filter_in_app_unread_notifications / filter_all_in_app_unread_notifications
(unread), filter_in_app_notifications / filter_all_in_app_notifications (read + unread),
the count_in_app_notifications / count_in_app_unread_notifications counters, and the
idempotent, optionally user-scoped mark_sent_as_read_bulk. See the vintasend README for the
service-level in-app API (pagination, counts and bulk mark-as-read).