strprfcrm/app/Providers/FcmServiceProvider.php

<?php

namespace App\Providers;

use App\Services\Fcm\FcmChannel;
use App\Services\Fcm\FcmService;
use Illuminate\Notifications\ChannelManager;
use Illuminate\Support\ServiceProvider;

class FcmServiceProvider extends ServiceProvider
{
    public function register(): void
    {
        $this->app->singleton(FcmService::class);
    }

    public function boot(): void
    {
        $this->app->make(ChannelManager::class)->extend('fcm', function ($app) {
            return $app->make(FcmChannel::class);
        });
    }
}