I am no longer working on this as the new API is US-only as I'm in the UK, so cannot even use it or the new app. Please don't ask me questions about it as I honestly can't remember anything.
This is a work in progress, just jotting down my findings from the APK decompile so far. As I can only read the decompiled Java and not MITM the app due it not working in the UK, getting the payload info may take a while. There's loads of API calls so this may not be thorough for a while.
Base URL: https://icm.infinitiusa.com/NissanLeafProd/rest