Extended functionality examples

We need to extend examples. I personally need this functionality, and it will simplify the learning curve for everyone.

- Postgres Login/Signup
- Social Login/SIgnup
- Form upload, including file upload (using streams)
- Application change event subscription on frontend
- Communication between websockets
- Credentials check on server side, to verify permission to access specific application RPCs

The issue names no files, tests, or entry points and combines several areas: PostgreSQL and social login, streamed uploads, frontend change subscriptions, websocket communication, and server-side RPC permission checks. Start by locating the existing examples for the relevant Node.js and frontend functionality and determine which requested area can be scoped independently. Done would require adding and documenting the agreed examples, with verification for each supported flow.

Written by the indexing model from the issue text.