0.15.3

• Added OneToOneField implementation:

  OneToOneField describes a one to one relation between two models.
  It can be set from the primary side only, but resolved from both sides in the same way.

  describe_model(...) now also reports OneToOne relations in both directions.

  Usage example:

   event: fields.OneToOneRelation[Event] = fields.OneToOneField(
       "models.Event", on_delete=fields.CASCADE, related_name="address"
   )

• Prefetching is done concurrently now, sending all prefetch requests at the same time instead of in sequence.
• Enabe foreign key enforcement on SQLite for builds where it was optional.