app-backend: migrate to use static configuration and extension point

Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>

plugins/app-backend/package.json

@@ -49,6 +49,7 @@
     "@backstage/backend-plugin-api": "workspace:^",
     "@backstage/config": "workspace:^",
     "@backstage/config-loader": "workspace:^",
+    "@backstage/plugin-app-node": "workspace:^",
     "@backstage/types": "workspace:^",
     "@types/express": "^4.17.6",
     "express": "^4.17.1",
@@ -73,8 +74,10 @@
     "node-fetch": "^2.6.7",
     "supertest": "^6.1.3"
   },
+  "configSchema": "config.d.ts",
   "files": [
     "dist",
+    "config.d.ts",
     "migrations/**/*.{js,d.ts}",
     "static"
   ]