[DOCS] Firebase idToken and Cloud Function Authorization

### Firebase idToken and Cloud Function Authorization

I was looking to this documentation:
- https://github.com/firebase/functions-samples/tree/main/authenticated-json-api
- https://github.com/firebase/functions-samples/tree/main/authorized-https-endpoint

Both documentation are not clear about the following cenario.

I have a user authenticated on firebase and a Firebase IdToken.

When I create a Cloud Function and deploy it to GCP without the allUsers invoker role I always get a 403 response.

It looks like the Firebase idToken is not recognized by GCP Cloud Function IAM handler.

Is there a missing role configuration? Or should I do some other configuration?

Note: I want to avoid using the allUsers invoke rule