Support for disabling Battery Optimization

We could add a feature in CAMS where the user is taken to the Settings on the phone for disabling battery optimization, like this:

Also take a look at the notes on the [wiki on background sensing](https://github.com/carp-dk/carp.sensing-flutter/wiki/6.-Best-Practice#background-sensing).

Can use the [app_settings](https://pub.dev/packages/app_settings) package