Refactor Game Modes (#5857)

Content.Server/GameTicking/Rules/SandboxRuleSystem.cs

@@ -0,0 +1,21 @@
+using Content.Server.Sandbox;
+using Robust.Shared.IoC;
+
+namespace Content.Server.GameTicking.Rules;
+
+public class SandboxRuleSystem : GameRuleSystem
+{
+    [Dependency] private readonly ISandboxManager _sandbox = default!;
+
+    public override string Prototype => "Sandbox";
+
+    public override void Added()
+    {
+        _sandbox.IsSandboxEnabled = true;
+    }
+
+    public override void Removed()
+    {
+        _sandbox.IsSandboxEnabled = false;
+    }
+}