Jetstream 'identity' events are emitted every time a DID's handle
changes; the 'account' variant sometimes carries the verified
handle too. The AppView was logging both kinds as 'identity event
(logged only)' and 'account event (logged only)' — discarding the
attached handle.
Now we extract 'identity.handle' (falling back to
'account.handle'), and run it through a new
'indexer::backfill_handle(db, did, handle)'. The
'WHERE handle IS DISTINCT FROM $1' guard makes the UPDATE a
no-op when the value is already correct, so concurrent PDS
ingests and identity replays never fight.
End-of-stale-state: existing rows whose 'identity' event fired
before this code shipped will still be empty. Those get back-filled
over time as DIDs re-emit identity events, plus the 5-minute
handle-sync worker (next commit) handles the bulk for the rest.
tomdebone
73e56fd788