adding support for self check and db updat ewith zip files

src/client_backend/update.h

@@ -4,6 +4,7 @@
 #include <curl/curl.h>
 #include<string>
 int update_db(const std::string& folder_path);
+int update_db2(const std::string& folder_path);
 int update_settings(const std::string& settings_type);
 int action_update_settings();
 int action_update_db();