Fix case sensitivity for http header (#283)

Author: chr-hertel

src/Client/Transport/HttpTransport.php

@@ -122,7 +122,7 @@ public function send(string $data): void
             $this->logger->debug('Received session ID', ['session_id' => $this->sessionId]);
         }
 
-        $contentType = $response->getHeaderLine('Content-Type');
+        $contentType = strtolower($response->getHeaderLine('Content-Type'));
 
         if (str_contains($contentType, 'text/event-stream')) {
             $this->activeStream = $response->getBody();

src/Server/Transport/Http/Middleware/AuthorizationMiddleware.php

@@ -166,7 +166,7 @@ private function applyAttributes(ServerRequestInterface $request, array $attribu
 
     private function parseBearerToken(string $authorization): ?string
     {
-        if (!preg_match('/^Bearer\\s+(.+)$/', $authorization, $matches)) {
+        if (!preg_match('/^Bearer\\s+(.+)$/i', $authorization, $matches)) {
             return null;
         }
 

src/Server/Transport/Http/Middleware/ClientRegistrationMiddleware.php

@@ -70,7 +70,7 @@ public function process(ServerRequestInterface $request, RequestHandlerInterface
     private function handleRegistration(ServerRequestInterface $request): ResponseInterface
     {
         $contentType = $request->getHeaderLine('Content-Type');
-        if (!str_starts_with($contentType, 'application/json')) {
+        if (!str_starts_with(strtolower($contentType), 'application/json')) {
             return $this->jsonResponse(400, [
                 'error' => 'invalid_client_metadata',
                 'error_description' => 'Content-Type must be application/json.',