painfull usage without android iap

[qeepcologne]

usage without android.billingclient is very painfull (and undocumented):
first i had to ignore in proguard-rules.pro to compile the app:
-dontwarn com.android.billingclient.api.**
then fix app initialization error via adding empty dummy inteface
android/app/src/main/java/com/android/billingclient/api

package com.android.billingclient.api;

public interface PurchasesUpdatedListener {
}

i can't understand that optional feature has these hard depency.
(issue is not new, i tested with 1.5.0 and 1.6.0).