Add Psr\Http\Client\ClientInterface to Service Container

[Jimbolino]

When writing code, I often inject my PSR dependencies like this:

    public function log(\Psr\Log\LoggerInterface $log)
    {
        $log->info('some info');
        var_dump($log::class); // Illuminate\Log\LogManager
    }

    public function cache(\Psr\SimpleCache\CacheInterface $cache)
    {
        $cache->set('someKey', 'someValue');
        var_dump($cache::class); // Illuminate\Cache\Repository
    }

This works great, and i love Laravel for making it so easy to use dependency injection :)

However what i really miss is a nice way to inject a PSR-18 HTTP Client, for example like this:

    public function client(\Psr\Http\Client\ClientInterface $client)
    {
        $res = $client->get('https://example.com')->getReasonPhrase();
        var_dump($res); // "OK"
        var_dump($client::class); // GuzzleHttp\Client
    }

Since guzzle is a composer suggestion, and most people will have it installed. I think it would be nice to have something like this in the framework:

        if (class_exists(\GuzzleHttp\Client::class)) {
            app()->bind(\Psr\Http\Client\ClientInterface::class, function ($app) {
                return new \GuzzleHttp\Client();
            });
            app()->alias(\Psr\Http\Client\ClientInterface::class, 'http.client');
        }