1. Adapt the location callback in WeatherWorker to coroutines
2. Merge EventListenerJob into UpdateCalendarWorker
3. Remove BatteryListenerJob, as it's impossible to use Jobs to detect battery status
1. Replace foreground services with Workers
2. Support approximate location
3. Fallback to inexact alarms if the SCHEDULE_EXACT_ALARM permission is revoked
4. Specify the mutability of each PendingIntent
5. Explicitly declare the android:exported attribute for app components that use intent filters
1. UpdateCalendarService will fetch all events from now to the next fetch time + Preferences.showUntil, so that EventRepository holds all events need to be shown before the next fetch;
2. Every event is updated 1 minute after the corresponding time span, to make the actual time difference consistent with the displayed getRelativeTimeSpanString;
3. Update events only when necessary, eliminate redundant alarms; cancel all update alarms when showEvents is turned off.
