I have followed the advice of other SO solution:
1. Make my class Serializeable
2. Have a default constructor for Firebase
3. Update my proguard rules (Not sure about this o
you can easily use a data class, it already comes with an empty constructor ect.
@IgnoreExtraProperties
data class User(
var displayName: String? = null,
var email: String? = null,
var photoUrl : String? = null,
var userId: String? = null
)