refactor: Split off ServerInitializer.

src/init/ServerInitializer.ts

@@ -0,0 +1,20 @@
+import type { HttpServerFactory } from '../server/HttpServerFactory';
+import { Initializer } from './Initializer';
+
+/**
+ * Creates and starts an HTTP server.
+ */
+export class ServerInitializer extends Initializer {
+  private readonly serverFactory: HttpServerFactory;
+  private readonly port: number;
+
+  public constructor(serverFactory: HttpServerFactory, port: number) {
+    super();
+    this.serverFactory = serverFactory;
+    this.port = port;
+  }
+
+  public async handle(): Promise<void> {
+    this.serverFactory.startServer(this.port);
+  }
+}