#1462 extracted MapGrid's HasGravity property to separate Content com… (#4200)

* #1462 extracted MapGrid's HasGravity property to separate Content component

* #1462 - PR suggestions

* Merge to master

Co-authored-by: metalgearsloth <comedian_vs_clown@hotmail.com>

Content.Server/Gravity/GravityGeneratorComponent.cs

@@ -7,6 +7,7 @@ using Content.Shared.Interaction;
 using Robust.Server.GameObjects;
 using Robust.Server.Player;
 using Robust.Shared.GameObjects;
+using Robust.Shared.Map;
 using Robust.Shared.Serialization.Manager.Attributes;
 using Robust.Shared.ViewVariables;
 
@@ -108,6 +109,9 @@ namespace Content.Server.Gravity
             {
                 MakeOn();
             }
+
+            var msg = new GravityGeneratorUpdateEvent(Owner.Transform.GridID, Status);
+            Owner.EntityManager.EventBus.RaiseLocalEvent(Owner.Uid, msg);
         }
 
         private void HandleUIMessage(ServerBoundUserInterfaceMessage message)
@@ -163,4 +167,16 @@ namespace Content.Server.Gravity
             _appearance?.SetData(GravityGeneratorVisuals.CoreVisible, true);
         }
     }
+
+    public sealed class GravityGeneratorUpdateEvent : EntityEventArgs
+    {
+        public GridId GridId { get; }
+        public GravityGeneratorStatus Status { get; }
+
+        public GravityGeneratorUpdateEvent(GridId gridId, GravityGeneratorStatus status)
+        {
+            GridId = gridId;
+            Status = status;
+        }
+    }
 }