* Use local copies of pebble certs as docker image contains outdated versions
* Update the preferred chain used in Staging
* Put test API keys in github secrets, add code to create/delete test domains to prevent misuse
* Simplify dns_add_acmedns

Fix other workflows to ignore workflow changes

Auto-build .deb package

Use hard-coded default credentials for srvrco when GitHub secrets are
not installed.

This is a security issue for srvrco, but a fix seems to be difficult.

Avoids having to push, e.g. when adding a tag or updating credentials.

Note: To add the secrets to your repository on GitHub

Goto Actions -> Settings -> Secrets

New Repository Secret

Add DUCKDNS_TOKEN
Add DYNU_API_KEY