Add initial webserver sources

test/webserver_example/errorresponsehandler.h

@@ -0,0 +1,30 @@
+#pragma once
+
+// system includes
+#include <string_view>
+#include <string>
+#include <system_error>
+
+// 3rdparty lib includes
+#include <asio_webserver/responsehandler.h>
+
+// forward declarations
+class ClientConnection;
+
+class ErrorResponseHandler : public ResponseHandler
+{
+public:
+    ErrorResponseHandler(ClientConnection &clientConnection, std::string_view path);
+    ~ErrorResponseHandler() override;
+
+    void requestHeaderReceived(std::string_view key, std::string_view value) final;
+    void sendResponse() final;
+
+private:
+    void written(std::error_code ec, std::size_t length);
+
+    ClientConnection &m_clientConnection;
+    std::string m_path;
+
+    std::string m_response;
+};