Answering a call doesn't switch to the phone app when locked

@mterry, @saviq
What is the plan for the greeter/lockscreen in this case and is there something we can do short term to workaround the issue?

Basically when you "accept" a phone call when the screen is locked and the greeter is visible can we notify the shell to unlock and display the phone app?

The current plan is to open the phone app as the greeter user, with limited access to contacts (i.e. at most the person calling you).

The short term solution will probably be to hide the greeter when an app is focused behind it. Will investigate.

> The current plan is to open the phone app as the greeter user, with limited access to contacts (i.e. at most the person calling you).

I imagine this will only be the case for PIN / password-protected accounts? For unprotected accounts this should just take you to your full phone app?

The linked branch implements the temporary behaviour of always hiding the greeter onFocusRequested - so whenever an app is started behind the greeter, it will hide (which the incoming call currently be the only case when that's the case).

Later we will need to make sure that it only happens in connection to interaction with a notification? Do we have other cases where we should unlock when an app requests focus?

Probably not part of this bug, but I imagine the phone should lock when such a call was finished / the phone app should quit if it was invoked via an incoming call?