implement some of the trivial backend plugins

Signed-off-by: Fredrik Adelöw <freben@gmail.com>

plugins/proxy-backend/api-report.md

@@ -3,6 +3,7 @@
 > Do not edit this file. It is a report generated by [API Extractor](https://api-extractor.com/).
 
 ```ts
+import { BackendFeature } from '@backstage/backend-plugin-api';
 import { Config } from '@backstage/config';
 import express from 'express';
 import { Logger } from 'winston';
@@ -11,6 +12,15 @@ import { PluginEndpointDiscovery } from '@backstage/backend-common';
 // @public
 export function createRouter(options: RouterOptions): Promise<express.Router>;
 
+// @alpha
+export const proxyPlugin: (
+  options?:
+    | {
+        skipInvalidProxies?: boolean | undefined;
+      }
+    | undefined,
+) => BackendFeature;
+
 // @public (undocumented)
 export interface RouterOptions {
   // (undocumented)

plugins/proxy-backend/package.json

@@ -8,7 +8,8 @@
   "publishConfig": {
     "access": "public",
     "main": "dist/index.cjs.js",
-    "types": "dist/index.d.ts"
+    "types": "dist/index.d.ts",
+    "alphaTypes": "dist/index.alpha.d.ts"
   },
   "backstage": {
     "role": "backend-plugin"
@@ -24,7 +25,7 @@
   ],
   "scripts": {
     "start": "backstage-cli package start",
-    "build": "backstage-cli package build",
+    "build": "backstage-cli package build --experimental-type-build",
     "lint": "backstage-cli package lint",
     "test": "backstage-cli package test",
     "prepack": "backstage-cli package prepack",
@@ -33,6 +34,7 @@
   },
   "dependencies": {
     "@backstage/backend-common": "workspace:^",
+    "@backstage/backend-plugin-api": "workspace:^",
     "@backstage/config": "workspace:^",
     "@types/express": "^4.17.6",
     "express": "^4.17.1",
@@ -56,7 +58,8 @@
   },
   "files": [
     "dist",
-    "config.d.ts"
+    "config.d.ts",
+    "alpha"
   ],
   "configSchema": "config.d.ts"
 }

plugins/proxy-backend/src/index.ts

@@ -21,3 +21,4 @@
  */
 
 export * from './service';
+export { proxyPlugin } from './plugin';

plugins/proxy-backend/src/plugin.ts

@@ -0,0 +1,53 @@
+/*
+ * Copyright 2023 The Backstage Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { loggerToWinstonLogger } from '@backstage/backend-common';
+import {
+  createBackendPlugin,
+  coreServices,
+} from '@backstage/backend-plugin-api';
+import { createRouter } from './service/router';
+
+/**
+ * The proxy backend plugin.
+ *
+ * @alpha
+ */
+export const proxyPlugin = createBackendPlugin(
+  (options?: { skipInvalidProxies?: boolean }) => ({
+    id: 'proxy',
+    register(env) {
+      env.registerInit({
+        deps: {
+          config: coreServices.config,
+          discovery: coreServices.discovery,
+          logger: coreServices.logger,
+          httpRouter: coreServices.httpRouter,
+        },
+        async init({ config, discovery, logger, httpRouter }) {
+          httpRouter.use(
+            await createRouter({
+              config,
+              discovery,
+              logger: loggerToWinstonLogger(logger),
+              skipInvalidProxies: options?.skipInvalidProxies,
+            }),
+          );
+        },
+      });
+    },
+  }),
+);