`OutboxEventEmitter` resolved matching triggers and inserted outbox rows
through `Arc<dyn TriggerRepo>` / `Arc<dyn OutboxRepo>`, i.e. against the
pool — each query on whatever connection it happened to get. That makes a
transactional outbox impossible: the data write and the outbox rows can
never share a transaction, so a crash (or an outbox error) between them
silently loses the trigger event.
Take the emitter down to a connection instead of a pool:
* `outbox_repo::insert_on(exec, row)` and `trigger_repo::list_matching_on`
/ `list_matching_shared_on(exec, ...)` are generic over `PgExecutor`, so
the same SQL serves a pooled connection or a `&mut *tx`. The repo trait
methods delegate to them — the SQL keeps exactly one home.
* `emit_on` / `emit_shared_on` take a `&mut PgConnection` and run the whole
fan-out on it. The `ServiceEventEmitter` impl acquires one pooled
connection and calls them, so behaviour is unchanged today; a caller
holding a transaction can now pass `&mut *tx` and have the outbox rows
commit with the write.
* `OutboxEventEmitter::new` takes the `PgPool` directly (it was only ever
constructed once, in the host wiring).
Also collapses the three copy-pasted per-app match queries (kv/docs/files
differ only in the `kind` discriminator and detail table) and the three
`emit_*` bodies into one `plan()` + one match fn, so the suppression
anti-join, the chain walk, and the empty-ops-means-any-op semantic each
exist once rather than three times.
No behaviour change — pure refactor. It is the seam the transactional
write lands on next.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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