[8.x] Make accept header comparison case-insensitive (#39413)

* Make accept header comparison case-insensitive

* Update comment and ref link

* Update InteractsWithContentTypes.php

Co-authored-by: Taylor Otwell <taylor@laravel.com>

Concerns/InteractsWithContentTypes.php

@@ -35,7 +35,7 @@ public function wantsJson()
     {
         $acceptable = $this->getAcceptableContentTypes();
 
-        return isset($acceptable[0]) && Str::contains($acceptable[0], ['/json', '+json']);
+        return isset($acceptable[0]) && Str::contains(strtolower($acceptable[0]), ['/json', '+json']);
     }
 
     /**
@@ -60,6 +60,10 @@ public function accepts($contentTypes)
             }
 
             foreach ($types as $type) {
+                $accept = strtolower($accept);
+
+                $type = strtolower($type);
+
                 if ($this->matchesType($accept, $type) || $accept === strtok($type, '/').'/*') {
                     return true;
                 }
@@ -93,6 +97,10 @@ public function prefers($contentTypes)
                     $type = $mimeType;
                 }
 
+                $accept = strtolower($accept);
+
+                $type = strtolower($type);
+
                 if ($this->matchesType($type, $accept) || $accept === strtok($type, '/').'/*') {
                     return $contentType;
                 }