FEP-ef61: Portable Objects

Update: #240 - FEP-ef61: Update proposal - fediverse/fep - Codeberg.org

Switching to did:ap:key:

did:ap is a DID method that can be used to add DID URL functionality to other types of DIDs.

This change creates a boundary between identities (represented by ordinary DIDs) and data (did:ap and DID URLs). One can imagine similar constructions such as did:ap:web, did:ap:pkh and others.