Phase 1 step 3 — make NotificationsPublisher available via DI and
introduce the NOTIFICATIONS_ASYNC_ENABLED flag that will gate the
listener cutover.
- NotificationsAsyncConfig: tiny injectable that reads
NOTIFICATIONS_ASYNC_ENABLED (truthy: 1/true/yes/on, default disabled).
Callers don't touch process.env directly; per-category rollout can be
added later without churn in listeners.
- NotificationsModule providers/exports now include NotificationsPublisher
and NotificationsAsyncConfig so listeners/handlers can inject them.
- Tests (14 specs on the flag + 4 on the publisher = 18 total green):
* default disabled when unset
* truthy parsing (1, true, TRUE, yes, on, padded)
* falsy parsing (false, 0, no, off, empty, unknown)
* describe() reports human-readable state
No call sites updated yet — next commit migrates the first listener
(PaymentCompletedListener pilot) onto the publisher with the flag check.
Co-Authored-By: Paperclip <noreply@paperclip.ing>
b3836d8d0f