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

Relates #3 (closed)

terraform/.logan.yaml

-# .logan.yaml configures the logan tool to run terraform
-version: "1.2"
-project: "ucam-faas"
-image: "registry.gitlab.developers.cam.ac.uk/uis/devops/infra/dockerimages/logan-terraform:1.7"
-mount_docker_socket: true
-use_impersonation: true