Add alert for failed events after retry and fix broken cloud event exception handling

Relates #3 (closed)

terraform/modules/faas/main.tf

@@ -174,3 +174,16 @@ resource "google_pubsub_topic" "dead_letter" {
   name    = "${var.name}-dl"
   project = var.project
 }
+
+resource "google_pubsub_topic_iam_member" "publish_deadletter_topic" {
+  topic  = google_pubsub_topic.dead_letter.name
+  role   = "roles/pubsub.publisher"
+  member = "serviceAccount:${google_project_service_identity.pubsub_agent.email}"
+}
+
+
+resource "google_pubsub_subscription_iam_member" "deadletter_subscribe" {
+  subscription = google_pubsub_subscription.main[0].name
+  role         = "roles/pubsub.subscriber"
+  member       = "serviceAccount:${google_project_service_identity.pubsub_agent.email}"
+}