Allow apps to handle push notification interaction themselves

[provokateurin]

Currently we just open the corresponding app when the user click on the notification and we simply refresh the notifications bloc when a new one was received, but this is usually not enough:

neon/packages/neon_framework/lib/src/app.dart

Lines 111 to 149 in d39d597

	PushUtils.onPushNotificationReceived = (accountID) async {
	final account = _accountsBloc.accountByID(accountID);
	if (account == null) {
	return;
	}
	final allAppImplementations = NeonProvider.of<BuiltSet<AppImplementation>>(context);
	final app = allAppImplementations.tryFind(notifications.appID) as NotificationsAppInterface?;
	if (app == null) {
	return;
	}
	await _accountsBloc.getAppsBlocFor(account).getAppBloc<NotificationsBlocInterface>(app).refresh();
	};
	PushUtils.onLocalNotificationClicked = (pushNotificationWithAccountID) async {
	final account = _accountsBloc.accountByID(pushNotificationWithAccountID.accountID);
	if (account == null) {
	return;
	}
	_accountsBloc.setActiveAccount(account);
	final allAppImplementations = NeonProvider.of<BuiltSet<AppImplementation>>(context);
	final notificationsApp = allAppImplementations.tryFind(notifications.appID) as NotificationsAppInterface?;
	if (notificationsApp != null) {
	_accountsBloc
	.getAppsBlocFor(account)
	.getAppBloc<NotificationsBlocInterface>(notificationsApp)
	.deleteNotification(pushNotificationWithAccountID.subject.nid!);
	}
	final app = allAppImplementations.tryFind(pushNotificationWithAccountID.subject.app) ?? notificationsApp;
	if (app == null) {
	return;
	}
	await _openAppFromExternal(account, app.id);
	};

For example in Talk we actually want to open the room the push notification came from when it is clicked instead of just showing the room list.

The AppImplementation should be able to optionally implement two methods for handling these scenarios manually.