Code refactor, support multiple gateways and non-SAML authentication (#9)

* Code refactor

* Update README.md

GPClient/gatewayauthenticator.h

@@ -0,0 +1,44 @@
+#ifndef GATEWAYAUTHENTICATOR_H
+#define GATEWAYAUTHENTICATOR_H
+
+#include "portalconfigresponse.h"
+#include "normalloginwindow.h"
+#include "loginparams.h"
+#include <QObject>
+
+class GatewayAuthenticator : public QObject
+{
+    Q_OBJECT
+public:
+    explicit GatewayAuthenticator(const QString& gateway, const PortalConfigResponse& portalConfig);
+    ~GatewayAuthenticator();
+
+    void authenticate();
+
+signals:
+    void success(const QString& authCookie);
+    void fail(const QString& msg = "");
+
+private slots:
+    void onLoginFinished();
+    void onPreloginFinished();
+    void onPerformNormalLogin(const QString &username, const QString &password);
+    void onSAMLLoginFinished(const QMap<QString, QString> &samlResult);
+    void onLoginWindowRejected();
+
+private:
+    QString gateway;
+    QString preloginUrl;
+    QString loginUrl;
+
+    const PortalConfigResponse& portalConfig;
+
+    NormalLoginWindow *normalLoginWindow{nullptr};
+
+    void login(const LoginParams& params);
+    void doAuth();
+    void normalAuth(QString labelUsername, QString labelPassword, QString authMessage);
+    void samlAuth(QString samlMethod, QString samlRequest, QString preloginUrl = "");
+};
+
+#endif // GATEWAYAUTHENTICATOR_H