﻿Design, implement, and document a REST API for a simple bookmarks service:

1. Design: Define endpoints for CRUD operations on bookmarks (url, title, tags, created_at). Include search by tag.
2. Implement: Write the API using only Python standard library (http.server, json, urllib). No Flask, no FastAPI.
3. Document: Generate an OpenAPI 3.0 specification (YAML or JSON) for the implemented endpoints, including request/response schemas, status codes, and example values.

Include a self-contained test that starts the server, performs all CRUD operations, and verifies responses.
