Notification for logouts

[yatharthranjan]

Send a notification to users at least a day before the app automatically logs out due to expiry of the tokens. The notification will need to be rescheduled every time the token is refreshed.
To avoid inactive users from getting logged out, might also provide them incentive to look into donating data again.
This should be configurable per project, maybe through the protocol with default being disabled to keep existing functionality.