Click Drag Functionality + Refactor Interaction Interfaces (#1125)

Co-authored-by: Víctor Aguilera Puerto <6766154+Zumorica@users.noreply.github.com>
Co-authored-by: ComicIronic <comicironic@gmail.com>
Co-authored-by: Pieter-Jan Briers <pieterjan.briers+git@gmail.com>

Content.Server/Interfaces/GameObjects/Components/Interaction/IEquipped.cs

@@ -0,0 +1,62 @@
+using System;
+using Content.Shared.GameObjects.Components.Inventory;
+using JetBrains.Annotations;
+using Robust.Shared.GameObjects;
+using Robust.Shared.Interfaces.GameObjects;
+
+namespace Content.Server.Interfaces.GameObjects.Components.Interaction
+{
+    /// <summary>
+    ///     This interface gives components behavior when their owner is put in an inventory slot.
+    /// </summary>
+    public interface IEquipped
+    {
+        void Equipped(EquippedEventArgs eventArgs);
+    }
+
+    public class EquippedEventArgs : EventArgs
+    {
+        public EquippedEventArgs(IEntity user, EquipmentSlotDefines.Slots slot)
+        {
+            User = user;
+            Slot = slot;
+        }
+
+        public IEntity User { get; }
+        public EquipmentSlotDefines.Slots Slot { get; }
+    }
+
+    /// <summary>
+    ///     Raised when equipping the entity in an inventory slot.
+    /// </summary>
+    [PublicAPI]
+    public class EquippedMessage : EntitySystemMessage
+    {
+        /// <summary>
+        ///     If this message has already been "handled" by a previous system.
+        /// </summary>
+        public bool Handled { get; set; }
+
+        /// <summary>
+        ///     Entity that equipped the item.
+        /// </summary>
+        public IEntity User { get; }
+
+        /// <summary>
+        ///     Item that was equipped.
+        /// </summary>
+        public IEntity Equipped { get; }
+
+        /// <summary>
+        ///     Slot where the item was placed.
+        /// </summary>
+        public EquipmentSlotDefines.Slots Slot { get; }
+
+        public EquippedMessage(IEntity user, IEntity equipped, EquipmentSlotDefines.Slots slot)
+        {
+            User = user;
+            Equipped = equipped;
+            Slot = slot;
+        }
+    }
+}