We don't want to pull public container images that already exist. This
creates prevents pods from starting if there is any connectivity issue
with the upstream registry.
Using Kustomize, we can define the configuration file separately from
the Kubernetes resources, and use `configMapGenerators` to generate the
ConfigMap for it. Additionally, this will make it possible to update
_ntfy_ using `updatebot`.
Now that the reverse proxy that handles requests from the Internet uses
TLS pass-through, the Ingress for _ntfy_ needs to recognize both the
internal and external name.
*ntfy* allows notifications to include arbitrary file attachments. For
images, it will even show them in the notification. In order to support
this, the server must be configured with a writable filesystem location
to cache the files.