feat: Implement MongoDB orchestrator storage with registry, commands, and heartbeats

- Added NullAdvisoryObservationEventTransport for handling advisory observation events.
- Created IOrchestratorRegistryStore interface for orchestrator registry operations.
- Implemented MongoOrchestratorRegistryStore for MongoDB interactions with orchestrator data.
- Defined OrchestratorCommandDocument and OrchestratorCommandRecord for command handling.
- Added OrchestratorHeartbeatDocument and OrchestratorHeartbeatRecord for heartbeat tracking.
- Created OrchestratorRegistryDocument and OrchestratorRegistryRecord for registry management.
- Developed tests for orchestrator collections migration and MongoOrchestratorRegistryStore functionality.
- Introduced AirgapImportRequest and AirgapImportValidator for air-gapped VEX bundle imports.
- Added incident mode rules sample JSON for notifier configuration.

src/Excititor/StellaOps.Excititor.WebService/Program.cs

@@ -48,6 +48,7 @@ services.AddCsafNormalizer();
 services.AddCycloneDxNormalizer();
 services.AddOpenVexNormalizer();
 services.AddSingleton<IVexSignatureVerifier, NoopVexSignatureVerifier>();
+services.AddSingleton<AirgapImportValidator>();
 services.AddScoped<IVexIngestOrchestrator, VexIngestOrchestrator>();
 services.AddScoped<IVexObservationLookup, MongoVexObservationLookup>();
 services.AddOptions<ExcititorObservabilityOptions>()
@@ -140,6 +141,33 @@ app.MapGet("/excititor/status", async (HttpContext context,
 
 app.MapHealthChecks("/excititor/health");
 
+app.MapPost("/airgap/v1/vex/import", async (
+    [FromServices] AirgapImportValidator validator,
+    [FromServices] TimeProvider timeProvider,
+    [FromBody] AirgapImportRequest request,
+    CancellationToken cancellationToken) =>
+{
+    var errors = validator.Validate(request, timeProvider.GetUtcNow());
+    if (errors.Count > 0)
+    {
+        var first = errors[0];
+        return Results.BadRequest(new
+        {
+            error = new
+            {
+                code = first.Code,
+                message = first.Message
+            }
+        });
+    }
+
+    return Results.Accepted($"/airgap/v1/vex/import/{request.BundleId}", new
+    {
+        bundleId = request.BundleId,
+        generation = request.MirrorGeneration
+    });
+});
+
 app.MapPost("/v1/attestations/verify", async (
     [FromServices] IVexAttestationClient attestationClient,
     [FromBody] AttestationVerifyRequest request,