update index for ratings/prune old entries

small stat tweaks to add players on first kill/damage event
(instead of on connect which causes issues with slow writes)

SharedLibraryCore/Migrations/DatabaseContextModelSnapshot.cs

@@ -388,6 +388,8 @@ namespace SharedLibraryCore.Migrations
 
                     b.HasIndex("Performance", "Ranking", "When");
 
+                    b.HasIndex("When", "ServerId", "Performance", "ActivityAmount");
+
                     b.ToTable("EFRating");
                 });