Add threaded session backend architecture with real SSH backend

src/ssh_session_backend.h

@@ -0,0 +1,52 @@
+#ifndef ORBITHUB_SSH_SESSION_BACKEND_H
+#define ORBITHUB_SSH_SESSION_BACKEND_H
+
+#include "session_backend.h"
+
+#include <QProcess>
+#include <QString>
+#include <QTimer>
+
+class QTemporaryFile;
+
+class SshSessionBackend : public SessionBackend
+{
+    Q_OBJECT
+
+public:
+    explicit SshSessionBackend(const Profile& profile, QObject* parent = nullptr);
+    ~SshSessionBackend() override;
+
+public slots:
+    void connectSession(const SessionConnectOptions& options) override;
+    void disconnectSession() override;
+    void reconnectSession(const SessionConnectOptions& options) override;
+
+private slots:
+    void onProcessStarted();
+    void onProcessErrorOccurred(QProcess::ProcessError error);
+    void onProcessFinished(int exitCode, QProcess::ExitStatus exitStatus);
+    void onReadyReadStandardError();
+    void onConnectedProbeTimeout();
+
+private:
+    QProcess* m_process;
+    QTimer* m_connectedProbeTimer;
+    SessionState m_state;
+    bool m_userInitiatedDisconnect;
+    bool m_reconnectPending;
+    SessionConnectOptions m_reconnectOptions;
+    QString m_lastRawError;
+    QTemporaryFile* m_askPassScript;
+
+    void setState(SessionState state, const QString& message);
+    bool startSshProcess(const SessionConnectOptions& options);
+    bool configureAskPass(const SessionConnectOptions& options,
+                          QProcessEnvironment& environment,
+                          QString& error);
+    void cleanupAskPassScript();
+    QString mapSshError(const QString& rawError) const;
+    QString knownHostsFileForNullDevice() const;
+};
+
+#endif