handlers: Introduce HandlerVersion to return the verison string

handlers/handlerversion.h

@@ -0,0 +1,18 @@
+#ifndef HANDLERVERSION_H
+#define HANDLERVERSION_H
+#include "handler.h"
+class HandlerVersion : public Handler
+{
+  public:
+	using Handler::Handler;
+
+  public:
+	Response handleRequest(const Request &r) override;
+
+	bool canAccess(const Permissions &perms) override
+	{
+		return true;
+	}
+};
+
+#endif // HANDLERVERSION_H