[connectivity-service] Tell apps when network has changed

[Michael Terry]

= Background =

I have an app that controls Sonos speakers in your house. This is a brand of speaker that connects to your house's wifi and both exposes information (what is currently playing) and takes commands (play this song) over the network.

They have official apps for Android and iOS, but there are open source libraries for the protocol. So I'm making an Ubuntu app to control them.

= Problem =

My app wants to be able to detect when the connected network changes (4G->wifi, wifi->4G, wifi->different wifi), so that it knows when to scan for speakers on the network.

But currently, the only information exposed by the connectivity service is "online, connecting, offline" (or using the Qml plugin, just online/offline).

And when switching between networks (like 4G->wifi), the "online" status reasonably doesn't change. So my app never knows that something happened.

= Proposed Solution =

I understand that exposing information about wifi networks might leak location data to apps. But I don't need much. Merely a signal like "networkChanged" would be sufficient.