Added substitution date + default courses

BetterIServ.Backend/Entities/UnitsData.cs

@@ -1,6 +1,7 @@
 namespace BetterIServ.Backend.Entities; 
 
 public struct UnitsData {
+    public DateTime Date { get; set; }
     public IList<string> Notifications { get; set; }
     public IList<Substitution> Substitutions { get; set; }
 }