[FEP-0f2a]: Announce Activity for Migrations and Tombstone Events

PR open

This thread is mostly SHOULDs and pedantically-explicit explanations of how existing FEPs and existing AP/AS behaviors work together. Buried among the self-evident stuff are a few novel behaviors and ideas, but the main purpose was to make existing FEPs easier to test (see the attached specification for a Test Case, with sample implementation forthcoming).

This was informed by conversations with Lisa Dusseault who has been working on this much larger spec. Not sure what Lisa’s handle is on here.

For more context, see also the socialweb thread for FEP-7952 and the Actor-Relative URLs FEP.