Switch to FastAPI and move documentation

[anjackson]

FastAPI is a modern and widely-used framework for Python APIs with autogenerated OpenAPI documentation. This components could easily be switched to that, and used to generate the basic API docs. The detailed documentation, including examples etc., should be moved to ukwa-documentation where it can be edited and localised without messing with the live service.

• Use production style deployment under Docker, e.g. https://www.uvicorn.org/deployment/#gunicorn
• Add support for Prometheus multi-worker implementation. see e.g. prometheus_multiproc_dir and the Python client docs.
• Fix up screenshotting as per Add 'fast' mode, for quicker generation of screenshots for access/social cards webrender-puppeteer#19
• Add missing Crawls endpoint for live stats, and the corresponding redirect.
• Bring Save and Nominate together #13
• Expose UKWA entities, using IIIF concepts as appropriate #23
• Use httpx and iter_bytes consistently over requests https://www.python-httpx.org/async/ - prevents worker lockup.
• Decide whether to redirect, refuse or accept approximate timestamps for Mementos WARC requests
• Redirect IIIF image requests to the actual closest timestamp (and normalized URL?), to avoid making unnecessary screenshots and make the PIWD's accurate.
• Embed PWID as a metadata/link header in response.
• Add all safe and useful parameters to the CDX query API #43
• Review and fill out embedded API documentation. #42

[anjackson]

n.b. it means we can avoid the odd dependency on a fork of Flask-RESTx: https://github.com/anjackson/flask-restx in order to support HTTP 451 (#11 and https://github.com/anjackson/flask-restx/tree/patch-1 still awaiting python-restx/flask-restx#263)

[anjackson]

The fastapi branch has a work-in-progress implementation.

[anjackson]

Note this helpful advice on running FastAPI on Uvicorn behind NGINX https://www.uvicorn.org/deployment/

[anjackson]

The FAST API branch is now largely functional, and passes all but two tests from the (updated in coordination) API test suite.

The gaps are the crawl stats file, and that the Mementos WARC API just gives the closest match rather than redirecting to the closest match. See To Dos above.

[anjackson]

Okay, now live with the FastAPI version of the original services, but not everything outlined above has been done yet.