Tracking issue for peer IDs as CIDs

RFC: https://github.com/libp2p/specs/pull/209

This RFC outlines the process for moving from formatting peer IDs as base58 multihashes to formatting them as CIDs with a special libp2p-key multicodec (0x72).

This RFC does not change the in-memory and/or network representation of peer IDs, just the textual format.

This process has two stages that must be completed in order:

• Stage 1: Parse CIDs as peer IDs.
• Stage 2: Format peer IDs as CIDs by default.

Tracking status of all libp2p implementations:

• go-libp2p
  • Support the libp2p-key multicodec.
  • Support parsing CIDs as peer IDs.
    • PRs:
      • https://github.com/libp2p/go-libp2p-core/pull/41 released in v0.3.0
    • IPFS PRs (for discoverability):
      • go-ipfs support of CIDs in /ipns/ content paths (https://github.com/ipfs/go-ipfs/issues/5287)
  • Output peer IDs as CIDs by default
• js-libp2p
  • Support the libp2p-key multicodec.
    • PR https://github.com/multiformats/js-multicodec/pull/45, released in multicodec v0.5.2
  • Support parsing CIDs as peer IDs.
    • PRs:
      • https://github.com/libp2p/js-peer-id/pull/105
      • https://github.com/multiformats/js-multiaddr/pull/102
    • IPFS PRs (for discoverability):
      • feat: js-ipfs support of CIDs in /ipns/ content paths
  • Output peer IDs as CIDs by default
• rust-libp2p
  • Support the libp2p-key multicodec.
  • Support parsing CIDs as peer IDs.
  • Output peer IDs as CIDs by default
• java-libp2p
  • Support the libp2p-key multicodec.
  • Support parsing CIDs as peer IDs.
  • Output peer IDs as CIDs by default
• python-libp2p
  • Support the libp2p-key multicodec.
  • Support parsing CIDs as peer IDs.
  • Output peer IDs as CIDs by default

Start with the linked RFC in libp2p/specs#209, then review the checklist for go-libp2p, js-libp2p, rust-libp2p, java-libp2p, and python-libp2p. Check which implementations still lack the libp2p-key multicodec, CID parsing, or CID formatting; the tracking issue is done when the listed stages are completed across the implementations.