Add channel test providers for Email, Slack, Teams, and Webhook

- Implemented EmailChannelTestProvider to generate email preview payloads.
- Implemented SlackChannelTestProvider to create Slack message previews.
- Implemented TeamsChannelTestProvider for generating Teams Adaptive Card previews.
- Implemented WebhookChannelTestProvider to create webhook payloads.
- Added INotifyChannelTestProvider interface for channel-specific preview generation.
- Created ChannelTestPreviewContracts for request and response models.
- Developed NotifyChannelTestService to handle test send requests and generate previews.
- Added rate limit policies for test sends and delivery history.
- Implemented unit tests for service registration and binding.
- Updated project files to include necessary dependencies and configurations.

src/StellaOps.Excititor.WebService/Program.cs

@@ -32,7 +32,7 @@ services.AddCsafNormalizer();
 services.AddCycloneDxNormalizer();
 services.AddOpenVexNormalizer();
 services.AddSingleton<IVexSignatureVerifier, NoopVexSignatureVerifier>();
-services.AddSingleton<IVexIngestOrchestrator, VexIngestOrchestrator>();
+services.AddScoped<IVexIngestOrchestrator, VexIngestOrchestrator>();
 services.AddVexExportEngine();
 services.AddVexExportCacheServices();
 services.AddVexAttestation();
@@ -140,6 +140,23 @@ app.MapGet("/excititor/statements/{vulnerabilityId}/{productKey}", async (
     return Results.Ok(claims);
 });
 
+app.MapPost("/excititor/admin/backfill-statements", async (
+    VexStatementBackfillRequest? request,
+    VexStatementBackfillService backfillService,
+    CancellationToken cancellationToken) =>
+{
+    request ??= new VexStatementBackfillRequest();
+    var result = await backfillService.RunAsync(request, cancellationToken).ConfigureAwait(false);
+    var message = FormattableString.Invariant(
+        $"Backfill completed: evaluated {result.DocumentsEvaluated}, backfilled {result.DocumentsBackfilled}, claims written {result.ClaimsWritten}, skipped {result.SkippedExisting}, failures {result.NormalizationFailures}.");
+
+    return Results.Ok(new
+    {
+        message,
+        summary = result
+    });
+});
+
 IngestEndpoints.MapIngestEndpoints(app);
 ResolveEndpoint.MapResolveEndpoint(app);
 MirrorEndpoints.MapMirrorEndpoints(app);