Announce full connectivity only after DNS resolver is updated
Here's a motivation: the liferea RSS reader uses NM connectivity status to decide whether it can refresh feeds. So every time I open my laptop, liferea waits for the network to connect, and only then starts refreshing the feeds. And every single time this happens, all feeds are immediately marked with a red one-way sign indicating there's been an error refreshing them. That's because liferea refreshes the feeds before NM manages to tell systemd-resolved that the interface is up and what name servers to use.
I discussed this with Lubo over IRC and he told me that updating the connectivity status and updating the resolver configuration is done using g_idle_add and there's no explicit ordering between the two. I propose to explicitly delay the connectivity status announcement only after the resolver is updated and ready to answer queries.