Harden managed server deployment and authentication

dotnet/src/VoiceCat.Server/Transport/MediaRelay.cs

@@ -29,6 +29,7 @@ internal sealed class MediaRelay : IAsyncDisposable
     private readonly byte[] input = new byte[65535];
     private readonly MediaFanout fanout = new();
     private readonly Task receiving;
+    internal Task Completion => receiving;
     public IPEndPoint EndPoint { get; }
     public event Action<Exception>? Failed;