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/20201114232340_UpdateEFRatingIndex.cs

@@ -0,0 +1,22 @@
+using Microsoft.EntityFrameworkCore.Migrations;
+
+namespace SharedLibraryCore.Migrations
+{
+    public partial class UpdateEFRatingIndex : Migration
+    {
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.CreateIndex(
+                name: "IX_EFRating_When_ServerId_Performance_ActivityAmount",
+                table: "EFRating",
+                columns: new[] { "When", "ServerId", "Performance", "ActivityAmount" });
+        }
+
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropIndex(
+                name: "IX_EFRating_When_ServerId_Performance_ActivityAmount",
+                table: "EFRating");
+        }
+    }
+}