Re-organize all projects (#4166)

Content.Server/Tools/WelderSystem.cs

@@ -0,0 +1,33 @@
+using System.Collections.Generic;
+using System.Linq;
+using Content.Server.Tools.Components;
+using Robust.Shared.GameObjects;
+
+namespace Content.Server.Tools
+{
+    /// <summary>
+    ///     Despite the name, it's only really used for the welder logic in tools. Go figure.
+    /// </summary>
+    public class WelderSystem : EntitySystem
+    {
+        private readonly HashSet<WelderComponent> _activeWelders = new();
+
+        public bool Subscribe(WelderComponent welder)
+        {
+            return _activeWelders.Add(welder);
+        }
+
+        public bool Unsubscribe(WelderComponent welder)
+        {
+            return _activeWelders.Remove(welder);
+        }
+
+        public override void Update(float frameTime)
+        {
+            foreach (var tool in _activeWelders.ToArray())
+            {
+                tool.OnUpdate(frameTime);
+            }
+        }
+    }
+}