BodySystem stuff 2: overused boogaloo (#1174)

Co-authored-by: Pieter-Jan Briers <pieterjan.briers+git@gmail.com>

Content.Server/Health/BodySystem/IBodyPartContainer.cs

@@ -0,0 +1,19 @@
+using Robust.Shared.Interfaces.GameObjects;
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace Content.Server.BodySystem
+{
+
+    /// <summary>
+    ///     Making a class inherit from this interface allows you to do many things with it in the <see cref="ISurgeryData"/> class. This includes passing
+    ///     it as an argument to a <see cref="ISurgeryData.SurgeryAction"/> delegate, as to later typecast it back to the original class type. Every BodyPart also needs an
+    ///     IBodyPartContainer to be its parent (i.e. the BodyManagerComponent holds many BodyParts, each of which have an upward reference to it).
+    /// </summary>
+
+    public interface IBodyPartContainer
+    {
+
+    }
+}