This commit adds initial support for CallKit on supported platforms: iOS >= 10.
Since the call flow in Jitsi Meet is basically making outgoing calls, only
outgoing call support is currently handled via CallKit.
Features:
- "Green bar" when in a call.
- Native CallKit view when tapping on the call label on the lock screen.
- Support for audio muting from the native CallKit view.
- Support for recent calls (audio-only calls logged as Audio calls, others show
as Video calls).
- Call display name is room name.
- Graceful downgrade on systems without CallKit support.
Limitations:
- Native CallKit view cannot be shown for audio-only calls (this is a CallKit
limitaion).
- The video button in the CallKit view will start a new video call to the same
room, and terminate the previous one.
- No support for call hold.
Lyubo Marinov
Saúl Ibarra Corretgé