## Issue
312 Save notification on back navigation, enable filter on mobile
## Changes
- Don't clear then filter when mounted and there are unread notifications.
- We previously clear the filter because the user could be clicking the notification bell (which is showing some number) and we ended up with a blank page because of the filter.
- Allow the filter in mobile.
- Previously, it was intentionally removed for mobile (see bd42418f). I believe it was just because we don't have the style set up for mobile. Here's my quick attempt.
* fix type error
fix is subscribed check
- Persist subscription data locally
- add / remove subscription during log in / out
- Use store directly in hook
Add toast error if subscription fails
Revert removal of v2
hotfix linting issue
Add custom notification handler
- fix isSupported flag
- make icon color compatible with light/dark theme
- fix icon on notifications blocked banner
wip: add push notification banner to notifications page.
- ignore failed deletions via internal API
- add ua parsing package
- add more robust meta data to token save
refactor naming + add push toggle to notification button
shift some code around
update css naming o proper BEM notation
update notifications UI
remove now unneeded util function
Update push notification system to sue firebase sdk
separate service worker webpack bundling
update service worker to use firebase sdk
Add firebase config
Add firebase and remove filemanager
Stub out the basics for browser push notifications.
* fix safari
* try smaller image for badge
* add token validation with server, refactor code
* remove param
* add special icon for web notification badge
* add translations
* add missing trans for toast error
* add pushRequest method that will not prompt users who have subscribed but since disabled notifications in the settings.
- Re-organize the return statement of 'NotificationsPage' a bit, otherwise the entire page will reload (blink) every time the drop-down value is changed due to the 'fetching' flag.
- Retained the original behavior of (only showing a blank page + spinner) on the very first load. I think there is merit in not showing the buttons immediately (e.g. when not logged in and `/$/notifications` is accessed directly).
## Issue
Closes 5193: Add filtering on notifications page
## Approach
- Add a combo box, and simply filter out the notifications based on the combo box value.
- Selection state is persistent, but reset to All if there are unread ones when entering the page.
- Tell the user that "no notifications" could be due to the filter.
