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/StellaOps.Cli/Configuration/EgressPolicyHttpMessageHandler.cs

@@ -0,0 +1,51 @@
+using System;
+using System.Net.Http;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.Extensions.Logging;
+using StellaOps.AirGap.Policy;
+
+namespace StellaOps.Cli.Configuration;
+
+internal sealed class EgressPolicyHttpMessageHandler : DelegatingHandler
+{
+    private readonly IEgressPolicy? _policy;
+    private readonly ILogger _logger;
+    private readonly string _component;
+    private readonly string _intent;
+
+    public EgressPolicyHttpMessageHandler(IEgressPolicy? policy, ILogger logger, string component, string intent)
+    {
+        _policy = policy;
+        _logger = logger ?? throw new ArgumentNullException(nameof(logger));
+        _component = string.IsNullOrWhiteSpace(component) ? "stellaops-cli" : component;
+        _intent = string.IsNullOrWhiteSpace(intent) ? "cli-http" : intent;
+    }
+
+    protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
+    {
+        if (_policy is null || request.RequestUri is not { IsAbsoluteUri: true } uri)
+        {
+            return base.SendAsync(request, cancellationToken);
+        }
+
+        try
+        {
+            var egressRequest = new EgressRequest(
+                _component,
+                uri,
+                _intent,
+                operation: request.Method.Method);
+
+            _policy.EnsureAllowed(egressRequest);
+        }
+        catch (AirGapEgressBlockedException ex)
+        {
+            _logger.LogWarning(ex, "Egress blocked for {Component} when contacting {Destination}", _component, request.RequestUri);
+
+            throw;
+        }
+
+        return base.SendAsync(request, cancellationToken);
+    }
+}