@Entity
@Table(name = "shape")
@Inheritance(strategy = InheritanceType.JOINED)
abstract class Shape(

  @Id
  @JdbcTypeCode(SqlTypes.VARCHAR)
  @Column(name = "id", updatable = false, nullable = false, unique = true)
  open val id: UUID,

  @Length(max = 100)
  @Column(name = "name", nullable = false, length = 100)
  open var name: String,
)

@Entity
@Table(name = "rectangle")
@PrimaryKeyJoinColumn(name = "shape_id")
data class Rectangle(
  override val id: UUID,
  override var name: String,
) : Shape(id, name) 

val rectangle = Rectangle(
      id = UUID.randomUUID(),
      name = "Rectangle",
      color = Color.Red,
      properties = Properties("foo", "bar")
    )

em.persist(rectangle)