feat(module): WIP Release Candidate API

[davideast]

Checklist

• Issue number for this PR: Release Candidate API proposal! Breaking changes please read! #854
• Docs included?: // TODO:
• Test units included?: Yes
• In a clean directory, npm install, npm run build, and npm test run successfully? Yes

Description

See #854 for the complete story and discussion. Comments here should strictly be for code review.

Code sample

// TODO:

[cartant]

Would you consider renaming the authState property to user? Because that's what it is. If the underlying SDK entity is a firebase.User, how likely is it that authState will ever be anything other than a user? And if one of the goals of the RC is to co-exist with the SDK, shouldn't the two use the same terminology?

Having to use auth (in the beta) to refer to what is the user is a peeve of mine and I've seen the confusion that it causes in SO questions. If it has to be explained on SO, surely it's a problem.

[cartant]

Hmm, I should have waited until I'd had my morning coffee before posting the above comment. With FirebaseAuthState now gone, using authState as the name of the observable property seems fine. Please ignore my pre-coffee review.

[davideast]

@cartant I'm not so sure, it is an observable of user. But I guess that confusion could be that it can be null, and the null value is useful itself. That makes authState more suitable. @jsayol mentioned using just .state(). Thoughts?

[cartant]

authState is totally fine. As per my second comment, I wasn't paying close enough attention when I made the first. authState fits well with the SDK's onAuthStateChanged - which calls a function, passing the user. It's all good. I would have deleted my original comment had I been able to.