New Feature: Slot blockers (#35172)

* First commit

* More comments

* Update

* Update

* For Beloved Maintainers

* Beck T, my beloved

* Update

* Old stuff

* Update EquipAttemptEvents.cs

* Update UnequipAttemptEvent.cs

---------

Co-authored-by: beck-thompson <107373427+beck-thompson@users.noreply.github.com>

Content.Shared/Inventory/SlotBlockSystem.cs

@@ -0,0 +1,35 @@
+using Content.Shared.Inventory.Events;
+
+namespace Content.Shared.Inventory;
+
+/// <summary>
+/// Handles prevention of items being unequipped and equipped from slots that are blocked by <see cref="SlotBlockComponent"/>.
+/// </summary>
+public sealed partial class SlotBlockSystem : EntitySystem
+{
+    public override void Initialize()
+    {
+        base.Initialize();
+
+        SubscribeLocalEvent<SlotBlockComponent, InventoryRelayedEvent<IsEquippingTargetAttemptEvent>>(OnEquipAttempt);
+        SubscribeLocalEvent<SlotBlockComponent, InventoryRelayedEvent<IsUnequippingTargetAttemptEvent>>(OnUnequipAttempt);
+    }
+
+    private void OnEquipAttempt(Entity<SlotBlockComponent> ent, ref InventoryRelayedEvent<IsEquippingTargetAttemptEvent> args)
+    {
+        if (args.Args.Cancelled || (args.Args.SlotFlags & ent.Comp.Slots) == 0)
+            return;
+
+        args.Args.Reason = Loc.GetString("slot-block-component-blocked", ("item", ent));
+        args.Args.Cancel();
+    }
+
+    private void OnUnequipAttempt(Entity<SlotBlockComponent> ent, ref InventoryRelayedEvent<IsUnequippingTargetAttemptEvent> args)
+    {
+        if (args.Args.Cancelled || (args.Args.SlotFlags & ent.Comp.Slots) == 0)
+            return;
+
+        args.Args.Reason = Loc.GetString("slot-block-component-blocked", ("item", ent));
+        args.Args.Cancel();
+    }
+}