sanitize.php

<?php

use Illuminate\Support\Facades\Auth;
use App\Http\Controllers\Controller;

class SomeController extends Controller
{
    public function store()
    {
        $timesheet = request()->validate([
            'date' => ['required', 'date', 'before_or_equal:' . \Carbon\Carbon::today()],
            'records.*.project_id' => request()->sanitize('project_id', function ($projectId) {
//                ?
            }),
        ]);

        Auth::user()->timesheet()->save($timesheet);
    }
}