Laravel Socialite Providers Reddit 429 Too Many Requests - php

Question

I am using Socialite Providers for Reddit with Laravel 5.2. In an attempt to address a Reddit error ('too many requests') during authentication I am having difficulty overriding the Socialite Provider method to add a custom header ('User-Agent') to the authentication request.
Here are the details.
The original problem is that I am getting an error during authentication with Reddit:
ClientException in RequestException.php line 107:
Client error: `POST https://ssl.reddit.com/api/v1/access_token`
resulted in a `429 Too Many Requests` response:
{"error": 429}
I can fix the error by modifying the vendor/socialiteproviders\reddit\src\Provider.php method called getAccessToken to include a header called 'User-Agent'.
$response = $this->getHttpClient()->post($this->getTokenUrl(), [
'headers' => ['Accept' => 'application/json',
'User-Agent' => 'mydomain.com: v1.0 (by /u/reddituser)'],
'auth' => [$this->clientId, $this->clientSecret],
'form_params' => $this->getTokenFields($code),
]);
The problem with this solution is that my modifications can easily be lost with an update to the vendor files. Instead I would like to extend the Providers class and override the getAccessToken method.
I am able to get the ServiceProvider to register my custom method but I can't seem to get the custom method to actually run in place of the original.
Here is my code
app\Library\CustomRedditProvider.php (notice the dd which is never executed)
namespace app\Library\redditOverride;
use SocialiteProviders\Reddit\Provider;
class CustomRedditProvider extends Provider {
// public function getAccessToken($code)
public function getAccessToken($code)
{
dd('RedditCustomProvider getAccessToken');
$response = $this->getHttpClient()->post($this->getTokenUrl(), [
'headers' => ['Accept' => 'application/json',
'User-Agent' => 'mydomain.com: v1.0 (by /u/reddituser)'],
'auth' => [$this->clientId, $this->clientSecret],
'form_params' => $this->getTokenFields($code),
]);
$this->credentialsResponseBody = json_decode($response->getBody(), true);
return $this->parseAccessToken($response->getBody());
}
}
app/Providers/RedditOverrrideServiceProvider.php
namespace App\Providers;
use Illuminate\Support\ServiceProvider;
class RedditOverrideServiceProvider extends ServiceProvider
{
/**
* Bootstrap the application services.
*
* #return void
*/
public function boot()
{
//
}
/**
* Register the application services.
*
* #return void
*/
public function register()
{
$this->app['customredditprovider'] = $this->app->share(function($app)
{
return new CustomRedditProvider();
});
}
}
config/app.php
\SocialiteProviders\Manager\ServiceProvider::class,
App\Providers\RedditOverrideServiceProvider::class,
composer.json
"autoload": {
"classmap": [
"database",
"app/library"
],