Add force update option

[jacqueline8711]

At some point we may not want or can support an old version of the app.

An implementation example can be found here which uses remote config from Firebase.
Since this only works if the code is in the old version we don't want to support anymore we should implement this soon.
We can also use this to simply make the user aware that there is a new version if they haven't updated after a certain time and not necessarily force them to update if it is not necessary.

[thellmund]

Google is currently rolling out such a feature: In-app updates API

Do you think it would make sense to wait for that?

[jacqueline8711]

We should probably wait then. Thanks for pointing that out.
It's been 5 months since they announced it so hopefully it won't take too long to come out... I/O is soon...

[thellmund]

Seems to be available since I/O: https://joebirch.co/2019/05/07/exploring-in-app-updates-on-android/