support the new inertia once props feature. (Inertia::once)

[isaackearl]

Context

The Inertia integration in laravel-data is very good (thank you). Lazy::inertia() and Lazy::closure() cover most use cases well. However, Inertia v2 recently introduced https://inertiajs.com/partial-reloads#once-props (Inertia::once) which are resolved on the first visit, cached client-side, and excluded from subsequent responses (including redirects). There's currently no way to express this behavior inside a laravel-data DTO.

The Gap

• Lazy::closure() — resolved on every full visit, including redirects. Reliable, but re-queries data the client
  already has.
• Lazy::inertia() — only resolved on partial reloads. Efficient, but data is lost on redirects (e.g.
  back()->withErrors()) because it's excluded from full visits.
• Inertia::once() — resolved on first visit, cached client-side, excluded from subsequent responses. Ideal
  behavior, but can only be used at the controller level — not inside a DTO.

Use Case

Lookup data for forms (dropdowns that rarely change etc) is a good example. It's static during a session,
expensive to query, and needed across form submissions. Currently you either:

1. Use Lazy::closure() and accept redundant queries on every redirect
2. Move the data out of the DTO and use Inertia::once() at the controller level, breaking the DTO's
   encapsulation

Proposal

A Lazy::once() (or similar) that tells Inertia this prop should behave as a once prop — resolved on the first
visit and cached client-side:

class CaseShowResponse extends Data
{
public function __construct(
public int $id,
/** @var Lazy|DataCollection<int, EventTypeResponse> */
public Lazy|DataCollection $eventTypes,
) {}

  public static function fromModel(CaseRecord $case): self
  {
      return new self(
          id: $case->id,
          eventTypes: Lazy::once(fn () => EventTypeResponse::collect(
              EventType::query()->where('is_active', true)->get(),
              DataCollection::class
          )),
      );
  }

}