feat(delmia-notifier): connect-failure-only failover loop

src/ZB.MOM.WW.ScadaBridge.DelmiaNotifier/IRecipeSender.cs

@@ -0,0 +1,21 @@
+namespace ZB.MOM.WW.ScadaBridge.DelmiaNotifier;
+
+/// <summary>Whether a single POST attempt reached the server (<see cref="Connected"/>) or never did (<see cref="ConnectFailed"/>).</summary>
+internal enum AttemptKind
+{
+    Connected,
+    ConnectFailed,
+}
+
+/// <summary>Result of one POST attempt against a single base URL.</summary>
+/// <param name="Kind">Did the attempt reach the server?</param>
+/// <param name="StatusCode">HTTP status when <see cref="AttemptKind.Connected"/>; 0 otherwise.</param>
+/// <param name="Body">Parsed response body on a 2xx; null otherwise.</param>
+/// <param name="Error">Connection/exception detail when <see cref="AttemptKind.ConnectFailed"/>; null otherwise.</param>
+internal sealed record AttemptOutcome(AttemptKind Kind, int StatusCode, RecipeDownloadResult? Body, string? Error);
+
+/// <summary>Seam over a single recipe-download POST attempt, so the failover loop is testable without real HTTP.</summary>
+internal interface IRecipeSender
+{
+    Task<AttemptOutcome> SendAsync(string baseUrl, RecipeDownload payload, CancellationToken ct);
+}