WebhookResponse now carries a `warnings: list[str]` field. When the
subscription's URL starts with http://, an `insecure_url` advisory is
surfaced on every GET/CREATE without blocking the request. HMAC still
detects tampering regardless of transport — only read-confidentiality
is lost over plaintext — and test/dev environments without TLS stay
usable.
Matches the operator-trust posture already established by DA-06
(admin-on-admin protection is out of scope). The alternative — hard
rejection at admin time — was considered and declined; warning-plus-
visibility is the right shape.
THREAT_MODEL WH-03 accepted risk registered; revisit triggers are
multi-admin delegation, a regulated customer, or an operator ticket
asking for a DECNET_WEBHOOK_REQUIRE_HTTPS enforcement knob.
Introduces the webhook egress foundation — a new WebhookSubscription
table, admin-gated CRUD under /api/v1/webhooks, and the shared
delivery client that both the test-ping route and the upcoming worker
will use. No worker yet; this commit is API + model + client only.
Simple-mode enum (AttackerDetail / DeckyStatus / SystemStatus) expands
to bus-topic patterns at the router layer; storage is always the raw
pattern list. Advanced mode lets admins supply raw NATS-style patterns
directly. Filter-at-subscribe: the worker (next commit) will subscribe
to the union of patterns across enabled subscriptions.
Delivery client handles HMAC-SHA256 signing (X-DECNET-Signature),
retry on 429/5xx/network errors with jittered backoff, no-retry on
4xx. Secrets never leave the server on GET/LIST — only the create
response carries the secret for copy-out.
CRUD routes publish WEBHOOK_SUBSCRIPTIONS_CHANGED on the bus after
every mutation so the (future) worker can hot-reload.
Opens DEBT-037 for the deferred items (circuit breaker, dead-letter,
batch delivery, payload templates, secret-at-rest).
