feature/api-controller-improvements (#567)

* added error handler for api controller
* while downloading the config from the api, the Connecting status is now displayed
* added a button to delete container config for api servers
* added crc check to avoid re-import of api configs
* fixed currentIndex of serversMenuContent after DefaultServerIndexChanged
* added closing the import window after re-importing the config from api

client/ui/controllers/connectionController.h

@@ -26,6 +26,8 @@ public:
     QString connectionStateText() const;
 
 public slots:
+    void toggleConnection(bool skipConnectionInProgressCheck);
+
     void openConnection();
     void closeConnection();
 
@@ -45,6 +47,8 @@ signals:
     void connectionErrorOccurred(const QString &errorMessage);
     void reconnectWithUpdatedContainer(const QString &message);
 
+    void noInstalledContainers();
+
 private:
     Vpn::ConnectionState getCurrentConnectionState();