TenantAtlas/app/Providers/AppServiceProvider.php

<?php

namespace App\Providers;

use App\Services\Graph\GraphClientInterface;
use App\Services\Graph\MicrosoftGraphClient;
use App\Services\Graph\NullGraphClient;
use Illuminate\Support\ServiceProvider;

class AppServiceProvider extends ServiceProvider
{
    /**
     * Register any application services.
     */
    public function register(): void
    {
        $this->app->singleton(GraphClientInterface::class, function ($app) {
            $config = $app['config']->get('graph');

            $hasCredentials = ! empty($config['client_id'])
                && ! empty($config['client_secret'])
                && ! empty($config['tenant_id']);

            if (! empty($config['enabled']) && $hasCredentials) {
                return $app->make(MicrosoftGraphClient::class);
            }

            return $app->make(NullGraphClient::class);
        });
    }

    /**
     * Bootstrap any application services.
     */
    public function boot(): void
    {
        //
    }
}