dynamic_launcher_install
Description:
This function completes installation of a launcher so that the icon and name given in previous method calls will show up in the desktop environment's menu.
The desktop_file_id must be prefixed with the caller's app ID followed by a "." and suffixed with ".desktop".
The desktop_entry data need not include Icon= or Name= entries since these will be added by the portal, and the Exec= entry will 
      be rewritten to call the application with e.g. "flatpak run" depending on the sandbox status of the app.
Parameters:
| this | 
           a [class@Portal]  | 
      
| token | 
           a token acquired via a [method@Portal.dynamic_launcher_request_install_token] or [method@Portal.dynamic_launcher_prepare_install] call  | 
      
| desktop_file_id | 
           the .desktop file name to be used  | 
      
| desktop_entry | 
           the key-file to be used for the contents of the .desktop file  | 
      
Returns:
| 
           true if the installation was successful, false with throws set otherwise  |