Feature/kanidm allow ability to enable PKCE

src/Kanidm/Provider.php

@@ -34,12 +34,20 @@ protected function getBaseUrl(): string
             throw new InvalidArgumentException('Missing base URL value.');
         }
 
+        /**
+         * PKCE is the default in recent versions of Kanidm, and heavily encouraged
+         * to be enforced whenever possible.
+         */
+        if (!$this->usesPKCE() && $this->getConfig('enable_pkce')) {
+            $this->enablePKCE();
+        }
+
         return $baseUrl;
     }
 
     public static function additionalConfigKeys(): array
     {
-        return ['base_url'];
+        return ['base_url', 'enable_pkce'];
     }
 
     protected function getAuthUrl($state): string

src/Kanidm/README.md

@@ -16,6 +16,9 @@ Please see the [Base Installation Guide](https://socialiteproviders.com/usage/),
   'client_secret' => env('KANIDM_CLIENT_SECRET'),
   'redirect' => env('KANIDM_REDIRECT_URI'),
   'base_url' => env('KANIDM_BASE_URL'),
+
+  // Recommended for security reasons and is default for OAuth clients in Kanidm
+  'enable_pkce' => env('KANIDM_ENABLE_PKCE', true),
 ],
 ```