Infected contact alert

[nathanww]

Planned feature--users can get an alert when a recent contact tests positive

Proposed model

1. User configures a local health authority website as a data provider
2. Health authority obtains Bluetooth adderesses of devices associated with positive tests and publishes them on the website
3. App regularly downloads updated list and alerts if a recently seem address matches an address on the positive list.

[nathanww]

It now looks like the best way to do this will be to integrate it with the upcoming Apple/Google contact tracing protocol.