Feat: Add a POC Notion FDW with users read only

[romaingrx]

New Feature: Notion FDW

Overview

This pull request introduces a POC for a Notion FDW based on their REST API. The primary goal is to enable read-only integration with Notion, starting with the users endpoint as of now. This initial implementation serves as a foundation for future expansions to include additional endpoints.

Key Features

• Initial Support for Users Endpoint: The current implementation supports read-only access to the users endpoint with query pushdown capabilities.
• Testing: Includes a test server setup to mock Notion API responses configured in the .ci/docker-compose.yml file as well as the unit tests.
• Extensibility for Future Endpoints: The architecture is designed with extensibility in mind (heavily based on the Stripe FWD), to facilitate the addition of the other endpoints later.

Future Work

• Additional Endpoint Integration: Plan to extend support to other Notion API endpoints such as databases and pages, with read-only queries for the moment.

Local setup with the actual Notion API

As I am relatively new to Rust, I welcome any feedback on best practices, code efficiency, or general Rust idioms that could enhance the implementation.

[burmecia]

Thank you for the PR! Can you format the code so it can pass the CI check?

[romaingrx]

Hello, it should be all good now. Sorry, totally forgot to run clippy and fmt locally on the 2 PRs.

[burmecia]

Looks great! Could you also add links in docs/index.md and mkdocs.yaml, so the docs can be generated?