Add basic response factories and helpers

src/http/response/JSONResponseFactory.ts

@@ -0,0 +1,19 @@
+import {ResponseFactory} from "./ResponseFactory";
+import {Request} from "../lifecycle/Request";
+
+export function json(value: any): JSONResponseFactory {
+    return new JSONResponseFactory(value)
+}
+
+export class JSONResponseFactory extends ResponseFactory {
+    constructor(
+        public readonly value: any
+    ) { super() }
+
+    public async write(request: Request) {
+        request = await super.write(request)
+        request.response.setHeader('Content-Type', 'application/json')
+        request.response.body = JSON.stringify(this.value)
+        return request
+    }
+}