Support for Hotspot wifi captive portal via RFC 8910 and RFC 8908

[pparent]

Hi,

Just wanted to mention that a nice and easy addition to Ubuntu touch would be wifi captive portal via RFC 8910 and RFC 8908.

It is actually very simple:

1- When you get a DHCP lease in the wifi interface look for option 114
2- If there is a URL in option 114 it's an API, just make a simple HTTP GET request on this URL (no parameters or header)
3- The result will be a json, if it contains "captive"="true" and has an "user-portal-url" field then we should just open this "user-portal-url" in the browser and it will allow the user to authenticate to the captive portal and use the wifi!

Really I think that's any easy addition, I may try to contribute this inside the OS when I have time.

Ps: Adding a simple script in /etc/dhcp/dhclient-exit-hooks.d/ to do that should do the trick I guess.