Update HttpServer & AuthenticationSystem to use Javalin

src/main/java/emu/grasscutter/server/http/documentation/RootRequestHandler.java

@@ -4,11 +4,11 @@ import static emu.grasscutter.config.Configuration.DATA;
 import static emu.grasscutter.utils.Language.translate;
 
 import emu.grasscutter.Grasscutter;
-import emu.grasscutter.data.ResourceLoader;
 import emu.grasscutter.utils.FileUtils;
+import emu.grasscutter.utils.HttpUtils;
 import emu.grasscutter.utils.Utils;
-import express.http.Request;
-import express.http.Response;
+import io.javalin.http.Context;
+
 import java.io.File;
 import java.nio.charset.StandardCharsets;
 
@@ -27,15 +27,16 @@ final class RootRequestHandler implements DocumentationHandler {
     }
 
     @Override
-    public void handle(Request request, Response response) {
+    public void handle(Context ctx) {
         if (template == null) {
-            response.status(500);
+            ctx.status(500);
             return;
         }
 
         String content = template.replace("{{TITLE}}", translate("documentation.index.title"))
                 .replace("{{ITEM_HANDBOOK}}", translate("documentation.index.handbook"))
                 .replace("{{ITEM_GACHA_MAPPING}}", translate("documentation.index.gacha_mapping"));
-        response.send(content);
+        ctx.contentType(HttpUtils.MediaType._html.getMIME());
+        ctx.result(content);
     }
 }