feat(smarts3-server): Introduce native custom S3 server implementation (Smarts3Server) with routing, middleware, context, filesystem store, controllers and XML utilities; add SmartXml and AWS SDK test; keep optional legacy s3rver backend.

ts/classes/middleware-stack.ts

@@ -0,0 +1,43 @@
+import * as plugins from '../plugins.js';
+import type { S3Context } from './context.js';
+
+export type Middleware = (
+  req: plugins.http.IncomingMessage,
+  res: plugins.http.ServerResponse,
+  ctx: S3Context,
+  next: () => Promise<void>
+) => Promise<void>;
+
+/**
+ * Middleware stack for composing request handlers
+ */
+export class MiddlewareStack {
+  private middlewares: Middleware[] = [];
+
+  /**
+   * Add middleware to the stack
+   */
+  public use(middleware: Middleware): void {
+    this.middlewares.push(middleware);
+  }
+
+  /**
+   * Execute all middlewares in order
+   */
+  public async execute(
+    req: plugins.http.IncomingMessage,
+    res: plugins.http.ServerResponse,
+    ctx: S3Context
+  ): Promise<void> {
+    let index = 0;
+
+    const next = async (): Promise<void> => {
+      if (index < this.middlewares.length) {
+        const middleware = this.middlewares[index++];
+        await middleware(req, res, ctx, next);
+      }
+    };
+
+    await next();
+  }
+}