Add customizable `KID` for JWK

README.md

···
         'disabled' => false,
         'prefix' => '/atp/oauth/',
         'private_key' => env('ATP_OAUTH_PRIVATE_KEY'),
+        'kid' => env('ATP_OAUTH_KID', 'atp-client-key'),
     ],
 
     // HTTP client settings
···
 ATP_CLIENT_URL="https://myapp.com"
 ATP_CLIENT_REDIRECT_URI="https://myapp.com/auth/atp/callback"
 ATP_OAUTH_PRIVATE_KEY="base64-encoded-private-key"
+ATP_OAUTH_KID="atp-client-key"
 ATP_REFRESH_THRESHOLD=300
 ATP_HTTP_TIMEOUT=30
 ```
+
+The `ATP_OAUTH_KID` is the Key ID used in your JWKS endpoint. Some developers may require this to match a specific value. The default is `atp-client-key`.
 
 ## Credential Storage
 

config/client.php

···
         'disabled' => env('ATP_OAUTH_DISABLED', false),
         'prefix' => env('ATP_OAUTH_PREFIX', '/atp/oauth/'),
         'private_key' => env('ATP_OAUTH_PRIVATE_KEY'),
+        'kid' => env('ATP_OAUTH_KID', 'atp-client-key'),
         'scope' => env('ATP_OAUTH_SCOPE', 'atproto transition:generic'),
 
         'client_metadata' => [
···
             'sleep' => env('ATP_HTTP_RETRY_SLEEP', 100),
         ],
     ],
-];
+];

src/Crypto/JsonWebKeySet.php

···
     public static function load(): static
     {
         $key = \SocialDept\AtpClient\Auth\OAuthKey::load();
+        $kid = config('client.oauth.kid', 'key-1');
 
-        return (new static)->addKey($key->toJWK()->asPublic());
+        return (new static)->addKey($key->toJWK()->withKid($kid)->asPublic());
     }
 
     /**