How to set up app for Google Play automated prelaunch testing


We have an app we just recently published to the Play store, but it requires the user to authenticate.
For now, we are only supporting authentication through our own backend service, so no Google authentication is possible yet.

But in the Play Console, it is necessary to provide login credentials for automated pre-launch testing, and we have to provide resource names too.

My question is, how can I get the resource names from the .apk file after building the ionic application?