Notifications are shown for messages sent by the sender in channels

[nikkothari22]

Service worker doesn't have access to any variables or local storage.

1. Store the current user in IndexedDB
2. Service worker fetches current user ID from indexedDB to check whether to show a notification
3. Clear current user from indexedDB after logging out.

This needs to be done before implementing push notifications on web app to avoid notification hell.

[linear[bot]]

RAV-156 Notifications are shown for messages sent by the sender in channels