increaseSession method
Increases a session for MBAudience.
Implementation
Future<void> increaseSession() async {
SharedPreferences prefs = await SharedPreferences.getInstance();
int session = prefs.getInt('com.mumble.mburger.audience.session') ?? 0;
int newSession = session + 1;
await prefs.setInt('com.mumble.mburger.audience.session', newSession);
String key = _sessionDateKeyForSession(newSession);
await prefs.setInt(key, DateTime.now().millisecondsSinceEpoch);
await _clearOldSessionValues();
await startSession();
}