Issue #9: implement worker frame protocol

src/MxGateway.Server/Workers/WorkerFrameProtocolErrorCode.cs

@@ -0,0 +1,13 @@
+namespace MxGateway.Server.Workers;
+
+public enum WorkerFrameProtocolErrorCode
+{
+    Unknown = 0,
+    InvalidConfiguration = 1,
+    EndOfStream = 2,
+    MalformedLength = 3,
+    MessageTooLarge = 4,
+    InvalidEnvelope = 5,
+    ProtocolVersionMismatch = 6,
+    SessionMismatch = 7,
+}