Add a completion handler to TelemetryManager.send()

[mjalq]

A simple escaping completion handler would suffice.

This would be useful if I want the app to send one signal per day at most, while making sure that the signal was received by the server before blocking further attempts.

`

    if lastSignalSentDate != today {
        TelemetryManager.send("appUsed")
        //If the above line fails due to poor internet or an offline launch of the app, we have no way of knowing.
        lastSignalSentDate = today
        
    }

`

Purposed solution

`

    if lastSignalSentDate != today {
        TelemetryManager.send("appUsed") { didFail in
            
            if !didFail {
                lastSignalSentDate = today

            }
        }
        
    }

`