Actions System + UI (#2710)

Co-authored-by: Vera Aguilera Puerto <6766154+Zumorica@users.noreply.github.com>

Content.Shared/Actions/IInstantItemAction.cs

@@ -0,0 +1,28 @@
+using System;
+using Robust.Shared.Interfaces.GameObjects;
+using Robust.Shared.Interfaces.Serialization;
+
+namespace Content.Shared.Actions
+{
+    /// <summary>
+    /// Item action which does something immediately when used and has
+    /// no target.
+    /// </summary>
+    public interface IInstantItemAction : IItemActionBehavior
+    {
+
+        /// <summary>
+        /// Invoked when the instant action should be performed.
+        /// Implementation should perform the server side logic of the action.
+        /// </summary>
+        void DoInstantAction(InstantItemActionEventArgs args);
+    }
+
+    public class InstantItemActionEventArgs : ItemActionEventArgs
+    {
+        public InstantItemActionEventArgs(IEntity performer, IEntity item, ItemActionType actionType) :
+            base(performer, item, actionType)
+        {
+        }
+    }
+}