model.kt

data class ContactInfo(
    val name: PersonalName,
    val email: Email)


data class PersonalName(
    val firstname: NotEmptyString,
    val middleInitial: NotEmptyString?,
    val lastname: NotEmptyString){    
    ... // construction code here
}

sealed class Email(val value: String){
    data class Verified(private val email: Unverified): Email(email.value)
    class Unverified private constructor(value: String): Email(value){
       ... // construction code here
    }

}