Conditional map support (#5868)

Co-authored-by: E F R <602406+Efruit@users.noreply.github.com>
Co-authored-by: Paul Ritter <ritter.paul1@googlemail.com>

Content.Server/Maps/Conditions/HolidayMapCondition.cs

@@ -0,0 +1,22 @@
+using System.Linq;
+using Content.Server.Holiday;
+using Robust.Shared.GameObjects;
+using Robust.Shared.IoC;
+using Robust.Shared.Log;
+using Robust.Shared.Serialization.Manager.Attributes;
+using Robust.Shared.Serialization.TypeSerializers.Implementations.Custom.Prototype.List;
+
+namespace Content.Server.Maps.Conditions;
+
+public class HolidayMapCondition : GameMapCondition
+{
+    [DataField("holidays")]
+    public string[] Holidays { get; } = default!;
+
+    public override bool Check(GameMapPrototype map)
+    {
+        var holidaySystem = EntitySystem.Get<HolidaySystem>();
+
+        return Holidays.Any(holiday => holidaySystem.IsCurrentlyHoliday(holiday)) ^ Inverted;
+    }
+}