Improve code base.

Author: vuongxuongminh

src/AbstractExtractor.php

@@ -42,7 +42,7 @@ final public function extract(Request $request): ?array
         $bag = $request->{$this->requestBag};
         $value = $bag->get($this->itemName);
 
-        if (null === $value) {
+        if (false !== is_string($value)) {
             return null;
         }
 
@@ -55,7 +55,7 @@ final public function extract(Request $request): ?array
         return $payload;
     }
 
-    abstract protected function extractFromValue(mixed $value): ?array;
+    abstract protected function extractFromValue(string $value): ?array;
 
     final protected function extractFromBase64EncodedPayload(string $encodedPayload): ?array
     {

src/Base64HeaderExtractor.php

@@ -17,7 +17,7 @@ public function __construct(string $issuer, string $itemName)
         parent::__construct($issuer, 'headers', $itemName);
     }
 
-    protected function extractFromValue(mixed $value): ?array
+    protected function extractFromValue(string $value): ?array
     {
         return $this->extractFromBase64EncodedPayload($value);
     }

src/OriginTokenExtractor.php

@@ -21,7 +21,7 @@ public function __construct(string $issuer, string $requestBag, string $itemName
         parent::__construct($issuer, $requestBag, $itemName);
     }
 
-    protected function extractFromValue(mixed $value): ?array
+    protected function extractFromValue(string $value): ?array
     {
         $tokenParts = explode('.', $value, 3);