feat(server): Rework transport architecture and add StreamableHttpTransport (#49)

* feat(server): Rework transport architecture and add StreamableHttpTransport

- `Server::connect()` no longer contains a processing loop.
- `TransportInterface` is updated with `setMessageHandler()` and `listen()`.
- `StdioTransport` is updated to implement the new interface.
- A new, minimal `StreamableHttpTransport` is added for stateless HTTP.

* refactor(server): use  event-driven message handling

* feat(server): Introduce a formal session management system

* fix: ensure session elements are preserved when building server (regression from #46)

* refactor: consolidate HTTP example to use shared dependencies

* feat(server): Enhance message handling with session support

- Updated `TransportInterface` to use `onMessage` for handling incoming messages with session IDs.
- Refactored `Server`, `Handler`, and transport classes to accommodate session management using `Uuid`.
- Introduced methods for creating sessions with auto-generated and specific UUIDs in `SessionFactory` and `SessionFactoryInterface`.

* feat(server): Integrate session management in message handling

- Added session support to the `Server` and `Handler` classes, allowing for session data to be managed during message processing.
- Updated `TransportInterface` to include session context in the `send` method.
- Refactored various request handlers to utilize session information, ensuring proper session handling for incoming requests.
- Introduced a file-based session store for persistent session data management

* feat: Update session builder method to use set* instead of with*

* feat: Fix test compatibility with new session management architecture

* chore: apply code style fixes

* fix: remove deprecated SSE transport and resolve PHPStan issues

src/Server/RequestHandler/InitializeHandler.php

@@ -18,6 +18,7 @@ use Mcp\Schema\Request\InitializeRequest;
 use Mcp\Schema\Result\InitializeResult;
 use Mcp\Schema\ServerCapabilities;
 use Mcp\Server\MethodHandlerInterface;
+use Mcp\Server\Session\SessionInterface;
 
 /**
  * @author Christopher Hertel <mail@christopher-hertel.de>
@@ -35,11 +36,14 @@ final class InitializeHandler implements MethodHandlerInterface
         return $message instanceof InitializeRequest;
     }
 
-    public function handle(InitializeRequest|HasMethodInterface $message): Response
+    public function handle(InitializeRequest|HasMethodInterface $message, SessionInterface $session): Response
     {
         \assert($message instanceof InitializeRequest);
 
-        return new Response($message->getId(),
+        $session->set('client_info', $message->clientInfo->jsonSerialize());
+
+        return new Response(
+            $message->getId(),
             new InitializeResult($this->capabilities, $this->serverInfo),
         );
     }