Bug when using exists rule on multiple select and `modifyQueryUsing` about filament

[ryanmortier]

I believe the issue is because the loadStateFromRelationshipsUsing() is not applying the modified query constraint. This is likely because the saveRelationshipsUsing() is using sync which requires the entire array rather than only the validated data.

Ref:

filament/packages/forms/src/Components/CheckboxList.php

Lines 170 to 198 in 68c7c68

	$this->loadStateFromRelationshipsUsing(static function (CheckboxList $component, ?array $state): void {
	$relationship = $component->getRelationship();
	/** @var Collection $relatedModels */
	$relatedModels = $relationship->getResults();
	$component->state(
	// Cast the related keys to a string, otherwise Livewire does not
	// know how to handle deselection.
	//
	// https://github.com/filamentphp/filament/issues/1111
	$relatedModels
	->pluck($relationship->getRelatedKeyName())
	->map(static fn ($key): string => strval($key))
	->toArray(),
	);
	});
	$this->saveRelationshipsUsing(static function (CheckboxList $component, ?array $state) {
	$pivotData = $component->getPivotData();
	if ($pivotData === []) {
	$component->getRelationship()->sync($state ?? []);
	return;
	}
	$component->getRelationship()->syncWithPivotValues($state ?? [], $pivotData);
	});