title: Android Kotlin Room Entity data class should be var, val or don't care?
body: <p>I am trying to be conventional, that is why I am refactoring some Kotlin codes in an Android project last few days. 
  I looked at many Room entity data class example, but still not get the best practice of use of val/var in the context of Room. 
  I suspect that the suitable way should be val since it is at the persistence layer and DTO (Data Transfer Objects) should be created about these entities which can be modified.
  Can someone please assure or deny this hypothesis!?</p>