autocde2.0/app/Http/Resources/API/ProjectSimpleResource.php

<?php

namespace App\Http\Resources\API;

use Illuminate\Http\Request;
use Illuminate\Http\Resources\Json\JsonResource;

class ProjectSimpleResource extends JsonResource
{
    /**
     * Transform the resource into an array.
     *
     * @return array<string, mixed>
     */
    public function toArray(Request $request): array
    {
        return [
            'id' => $this->id,
            'name' => $this->name,
            'display_id'=>$this->display_id,
            'begin' => $this->begin,
            'end' => $this->end,
            'asset'=> $this->when($this->assets->isNotEmpty(),function (){
                return $this->assets->map(function ($asset){
                    return new SimpleAssetResource($asset);
                })->all();
            }),
        ];
    }
}