Requests background permissions.
When the request is done, callback will be called. You can then call [method@Portal.request_background_finish] to get the
results.
| this |
a [class@Portal] |
| parent |
parent window information |
| reason |
reason to present to user for request |
| commandline |
command line to autostart |
| flags |
options for this call |
| cancellable |
optional [class@Gio.Cancellable] |
| callback |
a callback to call when the request is done |
| user_data |
data to pass to |