Issue with Bluetooth audio and CameraKit

Dear Snap Team,

We believe there is a potential issue with using CameraKit for video recording when a Bluetooth headset is connected to an iPhone.

Precondition
Before starting a CameraKit session, we:

• configure the shared AVAudioSession instance to allow Bluetooth audio (HFP profile to enable capturing audio from the headset mic)

let session = AVAudioSession.sharedInstance()
try session.setCategory(
        AVAudioSession.Category.playAndRecord,
        mode: AVAudioSession.Mode.default,
         options: [.allowBluetooth])
try session.setActive(true, options: .notifyOthersOnDeactivation)

• configure an AVCaptureSession as follows:

let captureSession = AVCaptureSession()
captureSession.sessionPreset = .hd1920x1080
captureSession.usesApplicationAudioSession = true
captureSession.automaticallyConfiguresApplicationAudioSession = false

let audioDevice = AVCaptureDevice.default(for: .audio)
do {
  let audioInput = try AVCaptureDeviceInput(device: audioDevice!)
  if captureSession.canAddInput(audioInput) {
    captureSession.addInput(audioInput)
  } else {
    print("Could not add audio input to session")
  }
} catch {
  print("Could not create audio input")
}

• Initialise an AVSessionInput instance as
  let input = AVSessionInput(captureSession, true)
  Expected Result

• CameraKit uses an audio device from the preconfigured AVAudioSession and AVCaptureSession when recording a video (i.e. Bluetooth headset mic when AirPods are connected to the iPhone)

• CameraKit does not make any changes to AVAudioSession

• Once video recording is finished, the user can resume audio playback to their Bluetooth headset from Apple Music / Spotify
  Actual Result

• CameraKit ignores any configuration settings previously made to AVAudioSession and re-initialises it with options: [.defaultToSpeaker]

• CameraKit uses the built-in iPhone mic to record audio
• Audio playback to the Bluetooth headset cannot be resumed