in datastore/src/main/scala/magnolify/datastore/EntityType.scala [151:159]
override def fromEntity(v: Entity)(cm: CaseMapper): T =
caseClass.construct { p =>
val f = v.getPropertiesOrDefault(cm.map(p.label), null)
if (f == null && p.default.isDefined) {
p.default.get
} else {
p.typeclass.from(f)(cm)
}
}