Add unit tests for SBOM ingestion and transformation

- Implement `SbomIngestServiceCollectionExtensionsTests` to verify the SBOM ingestion pipeline exports snapshots correctly.
- Create `SbomIngestTransformerTests` to ensure the transformation produces expected nodes and edges, including deduplication of license nodes and normalization of timestamps.
- Add `SbomSnapshotExporterTests` to test the export functionality for manifest, adjacency, nodes, and edges.
- Introduce `VexOverlayTransformerTests` to validate the transformation of VEX nodes and edges.
- Set up project file for the test project with necessary dependencies and configurations.
- Include JSON fixture files for testing purposes.

src/Cli/__Tests/StellaOps.Cli.Tests/Configuration/EgressPolicyHttpMessageHandlerTests.cs

@@ -0,0 +1,63 @@
+using Xunit;
+using System;
+using System.Net;
+using System.Net.Http;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.Extensions.Logging.Abstractions;
+using StellaOps.AirGap.Policy;
+using StellaOps.Cli.Configuration;
+
+namespace StellaOps.Cli.Tests.Configuration;
+
+public sealed class EgressPolicyHttpMessageHandlerTests
+{
+    [Fact]
+    public async Task SendAsync_AllowsRequestWhenPolicyPermits()
+    {
+        var options = new EgressPolicyOptions
+        {
+            Mode = EgressPolicyMode.Sealed
+        };
+        options.AddAllowRule(example.com);
+
+        var policy = new EgressPolicy(options);
+        var handler = new EgressPolicyHttpMessageHandler(policy, NullLogger<EgressPolicyHttpMessageHandler>.Instance, cli, test)
+        {
+            InnerHandler = new StubHandler()
+        };
+
+        var client = new HttpClient(handler, disposeHandler: true);
+        var response = await client.GetAsync(https://example.com/resource, CancellationToken.None).ConfigureAwait(false);
+
+        Assert.Equal(HttpStatusCode.OK, response.StatusCode);
+    }
+
+    [Fact]
+    public async Task SendAsync_ThrowsWhenPolicyBlocksRequest()
+    {
+        var options = new EgressPolicyOptions
+        {
+            Mode = EgressPolicyMode.Sealed
+        };
+
+        var policy = new EgressPolicy(options);
+        var handler = new EgressPolicyHttpMessageHandler(policy, NullLogger<EgressPolicyHttpMessageHandler>.Instance, cli, test)
+        {
+            InnerHandler = new StubHandler()
+        };
+
+        var client = new HttpClient(handler, disposeHandler: true);
+
+        var exception = await Assert.ThrowsAsync<AirGapEgressBlockedException>(
+            () => client.GetAsync(https://blocked.example, CancellationToken.None)).ConfigureAwait(false);
+
+        Assert.Contains(AirGapEgressBlockedException.ErrorCode, exception.Message, StringComparison.OrdinalIgnoreCase);
+    }
+
+    private sealed class StubHandler : HttpMessageHandler
+    {
+        protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
+            => Task.FromResult(new HttpResponseMessage(HttpStatusCode.OK));
+    }
+}