Introduce a plugin system that lets datasets be browsed and imported from
external services directly in the UI.
- toolkit/dataset_sources/: base class, registry, and a CLI bridge that the
Next.js API routes call to list plugins, browse items, fetch thumbnails,
and build import job configs. Plugins live in extensions/ and self-register
from their __init__.py, so they are only loaded on demand.
- ui: a RemoteSourceBrowseModal plus /api/datasets/remote/* routes for
listing plugins, browsing, thumbnails, and importing, with the settings
page driven by each plugin's settings_schema.
The framework is plugin-agnostic; no plugin is bundled here.
Gaute Lindkvist