Godmode refactor (#14651)

Content.Shared/Damage/Systems/DamageableSystem.cs

@@ -159,6 +159,12 @@ namespace Content.Shared.Damage
                 return damage;
             }
 
+            var before = new BeforeDamageChangedEvent(damage);
+            RaiseLocalEvent(uid.Value, ref before);
+
+            if (before.Cancelled)
+                return null;
+
             // Apply resistances
             if (!ignoreResistances)
             {
@@ -283,6 +289,12 @@ namespace Content.Shared.Damage
         }
     }
 
+    /// <summary>
+    ///     Raised before damage is done, so stuff can cancel it if necessary.
+    /// </summary>
+    [ByRefEvent]
+    public record struct BeforeDamageChangedEvent(DamageSpecifier Delta, bool Cancelled=false);
+
     /// <summary>
     ///     Raised on an entity when damage is about to be dealt,
     ///     in case anything else needs to modify it other than the base