#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.Shared/Gravity/GravityComponent.cs

@@ -0,0 +1,62 @@
+using System;
+using Content.Shared.NetIDs;
+using Robust.Shared.GameObjects;
+using Robust.Shared.Log;
+using Robust.Shared.Players;
+using Robust.Shared.Serialization;
+using Robust.Shared.ViewVariables;
+
+namespace Content.Shared.Gravity
+{
+    [RegisterComponent]
+    public sealed class GravityComponent : Component
+    {
+        public override string Name => "Gravity";
+        public override uint? NetID => ContentNetIDs.GRAVITY;
+
+        [ViewVariables(VVAccess.ReadWrite)]
+        public bool Enabled
+        {
+            get => _enabled;
+            set
+            {
+                if (_enabled == value) return;
+                _enabled = value;
+                if (_enabled)
+                {
+                    Logger.Info($"Enabled gravity for {Owner}");
+                }
+                else
+                {
+                    Logger.Info($"Disabled gravity for {Owner}");
+                }
+                Dirty();
+            }
+        }
+
+        private bool _enabled;
+
+        public override ComponentState GetComponentState(ICommonSession player)
+        {
+            return new GravityComponentState(_enabled);
+        }
+
+        public override void HandleComponentState(ComponentState? curState, ComponentState? nextState)
+        {
+            base.HandleComponentState(curState, nextState);
+            if (curState is not GravityComponentState state) return;
+            Enabled = state.Enabled;
+        }
+
+        [Serializable, NetSerializable]
+        protected sealed class GravityComponentState : ComponentState
+        {
+            public bool Enabled { get; }
+
+            public GravityComponentState(bool enabled) : base(ContentNetIDs.GRAVITY)
+            {
+                Enabled = enabled;
+            }
+        }
+    }
+}