Copy Envelope.Headers to MassTransitEnvelope on write path

src/Testing/CoreTests/Runtime/Interop/MassTransitEnvelopeTests.cs

@@ -39,6 +39,9 @@ public void create_masstransit_envelope_from_envelope()
             Message = new object()
         };
 
+        envelope.Headers["color"] = "purple";
+        envelope.Headers["number"] = "1";
+
         var mtEnvelope = new MassTransitEnvelope(envelope);
 
         mtEnvelope.MessageId.ShouldBe(envelope.Id.ToString());
@@ -47,6 +50,9 @@ public void create_masstransit_envelope_from_envelope()
         mtEnvelope.SentTime.ShouldNotBeNull();
 
         mtEnvelope.ExpirationTime!.Value.ShouldBe(envelope.DeliverBy!.Value.DateTime);
+
+        mtEnvelope.Headers["color"].ShouldBe("purple");
+        mtEnvelope.Headers["number"].ShouldBe("1");
     }
 
     [Fact]

src/Wolverine/Runtime/Interop/MassTransit/MassTransitEnvelope.cs

@@ -41,6 +41,11 @@ public MassTransitEnvelope(Envelope envelope)
         {
             ExpirationTime = envelope.DeliverBy.Value.UtcDateTime;
         }
+
+        foreach (var header in envelope.Headers)
+        {
+            Headers[header.Key] = header.Value;
+        }
     }
 
     public string? MessageId { get; set; }