Package adaptation with new refresh token methodolgy

[mho22]

As indicated in the issue spatie/ray#86

Since mid 2021, there's no longer long-lived access token :

In the past, the Dropbox API used only long-lived access tokens. 
These are now deprecated, but will remain available as an option in the Developer 
console for compatibility until mid 2021.

Dropbox OAuth Link

In the documentation, it explains there's multiple important elements :

• The App Key
• The App Secret
• The Authorization Code
• The Refresh Token

We'll need the app_key, app_secret and refresh_token to call an endpoint giving us a newly generated access_token making this package a hundred percent useful.

Here's how I proceed :

You will still need to authorize the access to the Dropbox App manually using this link :

https://www.dropbox.com/oauth2/authorize?client_id<YOUR_APP_KEY>&response_type=code&token_access_type=offline

This will give you the authorization_code needed to retrieve a refresh_token with this curl request :

curl https://api.dropbox.com/oauth2/token -d code=<ACCESS_CODE> -d grant_type=authorization_code -u <APP_KEY>:<APP_SECRET>

Giving you access to the refresh_token needed in the DROPBOX_REFRESH_TOKEN indicated below . The other elements are available in your Dropbox App.

.env.example

DROPBOX_APP_KEY=
DROPBOX_APP_SECRET=
DROPBOX_REFRESH_TOKEN=
DROPBOX_TOKEN_URL=https://${DROPBOX_APP_KEY}:${DROPBOX_APP_SECRET}@api.dropbox.com/oauth2/token

config/filesystems.php

        'dropbox' => [
            'driver' => 'dropbox',
            'token_url' => env('DROPBOX_TOKEN_URL'),
            'refresh_token' => env('DROPBOX_REFRESH_TOKEN'),
        ],

app/Providers/DropboxServiceProvider.php

use Illuminate\Contracts\Foundation\Application;
use Illuminate\Filesystem\FilesystemAdapter;
use Illuminate\Support\Facades\Storage;
use Illuminate\Support\ServiceProvider;
use League\Flysystem\Filesystem;
use Spatie\Dropbox\Client as DropboxClient;
use Spatie\FlysystemDropbox\DropboxAdapter;
use GuzzleHttp\Client;


class DropboxServiceProvider extends ServiceProvider
{
    public function boot(): void
    {
        Storage::extend( 'dropbox', function( Application $app, array $config )
        {
            $resource = ( new Client() )->post( $config[ 'token_url' ] , [
                    'form_params' => [ 
                            'grant_type' => 'refresh_token', 
                            'refresh_token' => $config[ 'refresh_token' ] 
                    ] 
            ]);

            $accessToken = json_decode( $resource->getBody(), true )[ 'access_token' ];

            $adapter = new DropboxAdapter( new DropboxClient( $accessToken ) );

            return new FilesystemAdapter( new Filesystem( $adapter, $config ), $adapter, $config );
        });
    }
}

A PR in code and documentation should be interesting. Should I PR this ? The previous code is also indicated in the Laravel 10 Documentation - Custom Filesystems