Streamlined Provider ID retrieval

[mauriceackel]

I realized that provider IDs are sourced differently at different places in the code. The change streamlines the retrieval of provider IDs and now always uses the static PROVIDER_ID property instead of the object property providerId:

Old: new firebase.auth.GoogleAuthProvider().providerId

New: firebase.auth.GoogleAuthProvider.PROVIDER_ID

[baumblatt]

Hi @mauriceackel ,

Can you please change your PR to point to the next branch.

Best regards.

[mauriceackel]

Done, but it seems that I need to resolve some conflicts. I will try to do this later and give you an update

[mauriceackel]

@baumblatt The PR is refactored and should be fine now.

Best, Maurice