feat(auditlog): SiteAuditTelemetryActor + ISiteStreamAuditClient seam (#23)

src/ScadaLink.AuditLog/Site/Telemetry/ISiteStreamAuditClient.cs

@@ -0,0 +1,23 @@
+using ScadaLink.Communication.Grpc;
+
+namespace ScadaLink.AuditLog.Site.Telemetry;
+
+/// <summary>
+/// Mockable abstraction over the central site-stream gRPC client surface that
+/// <see cref="SiteAuditTelemetryActor"/> uses to push <see cref="AuditEventBatch"/>
+/// payloads. The production implementation (added in Bundle E host wiring)
+/// wraps the auto-generated <c>SiteStreamService.SiteStreamServiceClient</c>;
+/// unit tests substitute via NSubstitute against this interface so the actor
+/// never needs a live gRPC channel.
+/// </summary>
+public interface ISiteStreamAuditClient
+{
+    /// <summary>
+    /// Pushes <paramref name="batch"/> to the central <c>IngestAuditEvents</c>
+    /// RPC. The returned <see cref="IngestAck"/> carries the
+    /// <c>accepted_event_ids</c> the actor will flip to
+    /// <see cref="ScadaLink.Commons.Types.Enums.AuditForwardState.Forwarded"/>
+    /// in the site SQLite queue.
+    /// </summary>
+    Task<IngestAck> IngestAuditEventsAsync(AuditEventBatch batch, CancellationToken ct);
+}