Allow for eager loading models

[inxilpro]

Many events create or update models in their handle() method, and up until now, this could cause an N+1 issue if you were operating on a lot of events that all interact with the same model at the same time (either batch operations or replays).

This introduces a new #[EagerLoad] attribute that you can add to any protected model property of an event (they must be protected because the model shouldn't be serialized with the event data).

For example:

class UserPromotedToManager extends Event
{
  #[StateId(UserState::class)]
  public int $user_id;

  #[EagerLoad]
  protected User $user;

  public function handle()
  {
    // If the user wasn't eager-loaded, load it lazily
    $this->user ??= User::find($this->user_id);

    $this->user->update(['role' => 'manager']);
  }
}

When verbs encounters a batch of events that have EagerLoad attributes, it'll load them all in a single query and then push the results into the appropriate events.

🪄

[inxilpro]

Talked with Daniel about this and the decision is to change the clone behavior and then merge in.