Contact Tracing — CBPeripheralManager ignores CBAdvertisementDataServiceDataKey on startAdvertising()

[marcdownie]

The hypothetical contact tracing code cannot work on any version of Core Bluetooth, foreground or background, for any service UUID, since CBPeripheralManager ignores the CBAdvertisementDataServiceDataKey for the purposes of startAdvertising(). Since this data field is the a heart of the Google / Apple Contact Tracing system, competing implementations of BLE-based tracing systems will have to do something else. This restriction does not apply to Android.