[Feature Request][Firebase Database] support for @DocumentId just like Firestore

[risalfajar]

What feature would you like to see?

In Firestore there's @DocumentId, a useful annotation to assign document id to a class automatically. Can this be implemented for Firebase Database?

How would you use it?

data class User(
    @DocumentId val userId: String = ""
    // ... other fields
)

[google-oss-bot]

I couldn't figure out how to label this issue, so I've labeled it for a human to triage. Hang tight.

[argzdev]

Thanks for filing another feature request, @risalfajar. Our engineers will be sure to look at it once they have the time.