feat(udt-011): TimeProviderArgentinaExtensions.GetArgentinaToday cross-platform

src/api/SIGCM2.Application/Common/TimeProviderArgentinaExtensions.cs

@@ -0,0 +1,45 @@
+namespace SIGCM2.Application.Common;
+
+/// <summary>
+/// Extension methods for <see cref="TimeProvider"/> that expose Argentina-localized
+/// date helpers. Handles the UTC-3 offset cross-platform (IANA / Windows TZ IDs).
+///
+/// UDT-011: Cat2 fields (VigenciaDesde, etc.) must use civil Argentine date, never
+/// raw UTC, to avoid date-creep during the 22:00–23:59 window.
+/// </summary>
+public static class TimeProviderArgentinaExtensions
+{
+    // IANA TZ id — Linux / macOS / .NET 8+ on Windows with ICU
+    public const string ArgentinaTimeZoneId = "America/Argentina/Buenos_Aires";
+
+    // Windows built-in TZ id — fallback for environments without ICU
+    public const string ArgentinaTimeZoneIdWindows = "Argentina Standard Time";
+
+    private static readonly TimeZoneInfo ArgentinaTz = LoadArgentinaTz();
+
+    /// <summary>
+    /// Returns today's civil date in Argentina timezone, computed from the
+    /// <see cref="TimeProvider"/> UTC clock.
+    /// Safe in tests via <c>FakeTimeProvider</c>; safe in production via
+    /// <c>TimeProvider.System</c>.
+    /// </summary>
+    public static DateOnly GetArgentinaToday(this TimeProvider timeProvider)
+    {
+        var utcNow = timeProvider.GetUtcNow();
+        var argentinaNow = TimeZoneInfo.ConvertTime(utcNow, ArgentinaTz);
+        return DateOnly.FromDateTime(argentinaNow.DateTime);
+    }
+
+    private static TimeZoneInfo LoadArgentinaTz()
+    {
+        try
+        {
+            return TimeZoneInfo.FindSystemTimeZoneById(ArgentinaTimeZoneId);
+        }
+        catch (TimeZoneNotFoundException)
+        {
+            // Windows without ICU: fall back to built-in Windows TZ name
+            return TimeZoneInfo.FindSystemTimeZoneById(ArgentinaTimeZoneIdWindows);
+        }
+    }
+}