Dont strtoupper allowed headers

Author: barryvdh

src/CorsService.php

@@ -181,7 +181,7 @@ private function configureAllowedHeaders(Response $response, Request $request)
     {
         if ($this->options['allowedHeaders'] === true) {
             if ($this->options['supportsCredentials']) {
-                $allowHeaders = strtoupper($request->headers->get('Access-Control-Request-Headers'));
+                $allowHeaders = $request->headers->get('Access-Control-Request-Headers');
                 $this->varyHeader($response, 'Access-Control-Request-Headers');
             } else {
                 $allowHeaders = '*';

tests/CorsTest.php

@@ -104,7 +104,7 @@ public function it_returns_allow_headers_header_on_allow_all_headers_request_cre
         $response = $app->handle($request);
 
         $this->assertEquals(204, $response->getStatusCode());
-        $this->assertEquals('FOO, BAR', $response->headers->get('Access-Control-Allow-Headers'));
+        $this->assertEquals('Foo, BAR', $response->headers->get('Access-Control-Allow-Headers'));
         $this->assertEquals('Access-Control-Request-Headers', $response->headers->get('Vary'));
     }