Add another national day source since DOTY is broken

Calendar/Service/Models/NationalDay.cs

@@ -0,0 +1,31 @@
+using JetBrains.Annotations;
+using System.Diagnostics.CodeAnalysis;
+
+namespace ChrisKaczor.HomeMonitor.Calendar.Service.Models;
+
+[PublicAPI]
+public class NationalDay
+{
+    public required string Name { get; set; }
+    public required string Url { get; set; }
+    public required string Excerpt { get; set; }
+    public required string Type { get; set; }
+
+    [SetsRequiredMembers]
+    public NationalDay(HolidayCalendar.Item item)
+    {
+        Name = item.Name;
+        Url = item.Url;
+        Excerpt = item.Excerpt;
+        Type = item.Type;
+    }
+
+    [SetsRequiredMembers]
+    public NationalDay(DaysOfTheYear.Entry entry)
+    {
+        Name = entry.Name;
+        Url = entry.Url;
+        Excerpt = entry.Excerpt;
+        Type = entry.Type;
+    }
+}