Zero-rating access for firebase auth features

[MatasRut]

Hello, I'm trying to add zero-rating for certain urls that my app calls so that users can access them even when they no longer have mobile data or wifi. I'm facing a problem that user's cannot sign in using firebase in such cases as it's not zero-rated but I'm using the Firebase SDK and the interactions with firebase services are abstracted, I can't see what urls are being called and should be added to the zero-rated list.