Refactor req() function declaration in auth.hpp for consistency

Updated `req()` function declaration in `auth.hpp` to use `const std::string&` for parameters.

Author: SaSukiTB

auth.hpp

@@ -105,12 +105,10 @@ namespace KeyAuth {
 		responsedata response;
 		Tfa tfa;
 	private:
-		std::string sessionid, enckey;
-
-		static std::string req(std::string data, std::string url);
 
+		std::string sessionid, enckey;
+		static std::string req(const std::string& data, const std::string& url);
 		static void debugInfo(std::string data, std::string url, std::string response, std::string headers);
-
 		static void setDebug(bool value);