NetworkManager can check if a network interface has "internet access" by
invoking a HTTP request.
The URI used for connectivity checking in NetworkManager can be configured
manually in NetworkManager.conf:
[connectivity]
uri=http://portal-check.exmaple.com/nm-check.txt
Portal Helper provides an argument to pass the URI that should be opened.
If this argument is empty it uses http://nmcheck.gnome.org as a fallback.
Pass the URI configured in NetworkManager to Portal Helper instead of
an empty string.
Fixes#1313
Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/2228>
2d6b21357d