Store events and create deliveries in the delivery engine (closes #544)

The receiver, resubmit and replay handlers now read and check the
request and make one call. Engine.StoreEvent stores an event with a
pending delivery for each active target and the totals in one
transaction, then queues them; Engine.CreateReplay does the same for
one replay delivery. The handlers take *delivery.Engine, so the
Notifier interface and its bridge are gone, and the engine's notify is
no longer exported. Archives and CircuitBreakers stay because the
handler tests fake them. The tests that read a queued task moved to
the engine's tests; the handler tests use an engine that is never
started.

Model: opus-5-5

internal/handlers/handlers_test.go

@@ -30,33 +30,6 @@ import (
 	"sneak.berlin/go/webhooker/internal/session"
 )
 
-// recordingNotifier is a delivery.Notifier that records the tasks it
-// was handed, so a test can prove a handler queued the delivery it
-// claims to have queued — and, on the refusal paths, that it queued
-// nothing.
-type recordingNotifier struct {
-	mu    sync.Mutex
-	tasks []delivery.Task
-}
-
-func (n *recordingNotifier) Notify(tasks []delivery.Task) {
-	n.mu.Lock()
-	defer n.mu.Unlock()
-
-	n.tasks = append(n.tasks, tasks...)
-}
-
-// Tasks returns a copy of the recorded tasks.
-func (n *recordingNotifier) Tasks() []delivery.Task {
-	n.mu.Lock()
-	defer n.mu.Unlock()
-
-	out := make([]delivery.Task, len(n.tasks))
-	copy(out, n.tasks)
-
-	return out
-}
-
 // recordingArchives is an archive.Archives that records what it
 // was asked to do, so a test can prove that a deletion or rename
 // path reached the archive writers. After FailRenames, every
@@ -264,11 +237,12 @@ func newTestAppWithConfig(
 			database.NewWebhookDBManager,
 			healthcheck.New,
 			session.New,
-			func() *recordingNotifier {
-				return &recordingNotifier{}
-			},
-			func(n *recordingNotifier) delivery.Notifier {
-				return n
+			archive.NewWriters,
+			// The engine is built on a lifecycle that is never started,
+			// so no worker runs: every delivery the engine creates for a
+			// handler stays pending, where the test can read it.
+			func(p delivery.EngineParams) *delivery.Engine {
+				return delivery.New(fxtest.NewLifecycle(t), p)
 			},
 			func() *recordingArchives {
 				return &recordingArchives{}