Improves and cleans up TabletopSystem further. (#4633)

Content.Server/Tabletop/Components/TabletopGamerComponent.cs

@@ -0,0 +1,18 @@
+using Robust.Shared.Analyzers;
+using Robust.Shared.GameObjects;
+using Robust.Shared.Serialization.Manager.Attributes;
+
+namespace Content.Server.Tabletop.Components
+{
+    /// <summary>
+    ///     Component for marking an entity as currently playing a tabletop.
+    /// </summary>
+    [RegisterComponent, Friend(typeof(TabletopSystem))]
+    public class TabletopGamerComponent : Component
+    {
+        public override string Name => "TabletopGamer";
+
+        [DataField("tabletop")]
+        public EntityUid Tabletop { get; set; } = EntityUid.Invalid;
+    }
+}