NativeDtlsEngine.sendAlert

TlsProgress sendAlert(DtlsPeerState state,  AlertLevel level,
          AlertDescription description)

@safe

Build and send a DTLS alert record to a peer.

If the peer has active write AEAD keys, the alert is encrypted. Otherwise it is sent in the clear (epoch 0).

`state`	The peer state.
`level`	The alert level (WARNING or FATAL).
`description`	The alert description code.

TlsProgress.DONE if sent, TlsProgress.ERROR on failure.