Implement InMemory Transport Layer for StellaOps Router

- Added InMemoryTransportOptions class for configuration settings including timeouts and latency.
- Developed InMemoryTransportServer class to handle connections, frame processing, and event management.
- Created ServiceCollectionExtensions for easy registration of InMemory transport services.
- Established project structure and dependencies for InMemory transport library.
- Implemented comprehensive unit tests for endpoint discovery, connection management, request/response flow, and streaming capabilities.
- Ensured proper handling of cancellation, heartbeat, and hello frames within the transport layer.

tests/StellaOps.Router.Transport.InMemory.Tests/InMemoryChannelTests.cs

@@ -0,0 +1,108 @@
+using StellaOps.Router.Common.Enums;
+using StellaOps.Router.Common.Models;
+using StellaOps.Router.Transport.InMemory;
+using Xunit;
+
+namespace StellaOps.Router.Transport.InMemory.Tests;
+
+public class InMemoryChannelTests
+{
+    [Fact]
+    public async Task ToMicroservice_WritesAndReads()
+    {
+        // Arrange
+        using var channel = new InMemoryChannel("test-1");
+        var frame = new Frame
+        {
+            Type = FrameType.Request,
+            CorrelationId = "corr-1",
+            Payload = ReadOnlyMemory<byte>.Empty
+        };
+
+        // Act
+        await channel.ToMicroservice.Writer.WriteAsync(frame);
+        var readFrame = await channel.ToMicroservice.Reader.ReadAsync();
+
+        // Assert
+        Assert.Equal(FrameType.Request, readFrame.Type);
+        Assert.Equal("corr-1", readFrame.CorrelationId);
+    }
+
+    [Fact]
+    public async Task ToGateway_WritesAndReads()
+    {
+        // Arrange
+        using var channel = new InMemoryChannel("test-1");
+        var frame = new Frame
+        {
+            Type = FrameType.Response,
+            CorrelationId = "corr-1",
+            Payload = ReadOnlyMemory<byte>.Empty
+        };
+
+        // Act
+        await channel.ToGateway.Writer.WriteAsync(frame);
+        var readFrame = await channel.ToGateway.Reader.ReadAsync();
+
+        // Assert
+        Assert.Equal(FrameType.Response, readFrame.Type);
+        Assert.Equal("corr-1", readFrame.CorrelationId);
+    }
+
+    [Fact]
+    public void Dispose_CancelsLifetimeToken()
+    {
+        // Arrange
+        var channel = new InMemoryChannel("test-1");
+
+        // Act
+        channel.Dispose();
+
+        // Assert
+        Assert.True(channel.LifetimeToken.IsCancellationRequested);
+    }
+
+    [Fact]
+    public void Dispose_CompletesChannels()
+    {
+        // Arrange
+        var channel = new InMemoryChannel("test-1");
+
+        // Act
+        channel.Dispose();
+
+        // Assert
+        Assert.True(channel.ToMicroservice.Reader.Completion.IsCompleted);
+        Assert.True(channel.ToGateway.Reader.Completion.IsCompleted);
+    }
+
+    [Fact]
+    public void BoundedChannel_RespectsBufferSize()
+    {
+        // Arrange & Act
+        using var channel = new InMemoryChannel("test-1", bufferSize: 5);
+
+        // Assert - no exception means it was created successfully
+        Assert.NotNull(channel);
+    }
+
+    [Fact]
+    public void Instance_CanBeSetAndRetrieved()
+    {
+        // Arrange
+        using var channel = new InMemoryChannel("test-1");
+        var instance = new InstanceDescriptor
+        {
+            InstanceId = "inst-1",
+            ServiceName = "test-service",
+            Version = "1.0.0",
+            Region = "eu1"
+        };
+
+        // Act
+        channel.Instance = instance;
+
+        // Assert
+        Assert.Same(instance, channel.Instance);
+    }
+}