New download API for PyPI

[xmunoz]

The Python Package Index, a key platform for Python developers, has a browser interface, but most people use PyPI by hitting its API endpoints with client applications such as pip. PyPI has a minimal download API that does not implement many features that users have requested. The lack of a full-featured download API in Warehouse (the PyPI codebase) blocks many improvements, including:

• Light-bandwidth metadata-only API calls and JSON standardization that would enable better downloads, installations, dependency resolution features, and troubleshooting for pip and other clients
• RSS feeds that other platforms could reuse to get PyPI updates in user tooling
• Security notification feeds
• Caching for the bandersnatch mirroring client

We'd like to architect and implement a new Warehouse download API to support these features, and deprecate and decommission the old endpoints. This requires backend development work, technical writing, user experience research, and publicity and coordination work within Python's community.