Only restricting cache per age wasn't enough for instances with lots of
multimedia usage and high number of posts.
MaxEntries is also more effective on cleanup, and purgeOnQuotaError
advertise that Discourse cache can be purged if necessary.
https://developers.google.com/web/tools/workbox/guides/storage-quota
The special offline page with fetch interception in service worker
is only strongly required on Android ad a pre-req for PWAs
This is now strongly restricted only to Android while iOS PWA support
gets better
Long term if we build offline support we can unlock it more globally
* Feature: Push notifications for Android
Notification config for desktop and mobile are merged.
Desktop notifications stay as they are for desktop views.
If mobile mode, push notifications are enabled.
Added push notification subscriptions in their own table, rather than through
custom fields.
Notification banner prompts appear for both mobile and desktop when enabled.
