feat: backend service

backend/internal/notification/errors.go

@@ -0,0 +1,22 @@
+package notification
+
+import "errors"
+
+// ErrNotificationNotFound is returned by AdminGetNotification when no
+// row matches the supplied identifier. Handlers map it to HTTP 404.
+var ErrNotificationNotFound = errors.New("notification: notification not found")
+
+// ErrUnknownKind is returned by Submit when the intent's Kind is not in
+// the catalog (`backend/README.md` §10). Submit does not surface it to
+// the producer — it persists a malformed-intent record and returns nil.
+// The exported sentinel exists so the package internals can branch on it.
+var ErrUnknownKind = errors.New("notification: unknown kind")
+
+// ErrEmptyIdempotencyKey is returned by Submit when the intent does not
+// carry an idempotency_key. Same surface treatment as ErrUnknownKind.
+var ErrEmptyIdempotencyKey = errors.New("notification: idempotency_key must be non-empty")
+
+// ErrNoRecipients is returned by Submit when a kind that requires user
+// recipients arrives without any. Same surface treatment as
+// ErrUnknownKind.
+var ErrNoRecipients = errors.New("notification: at least one recipient is required")