rename as ToEnvelopeKey

EnvelopeGenerator.Tests.Application/HistoryTests.cs

@@ -32,7 +32,7 @@ public class HistoryTests : TestBase
         var createReceiverCmd = this.CreateReceiverCommand();
         (var receiver, _) = await Mediator.Send(createReceiverCmd);
 
-        var key = (envelope.Uuid, receiver.Signature).EncodeEnvelopeReceiverId();
+        var key = (envelope.Uuid, receiver.Signature).ToEnvelopeKey();
 
         var createCmd = Fake.Provider.CreateHistoryCommand(key);