introduce standard docker workflow and include sbom in container images

[mac641]

Description

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The container image `metalstack/builder` is not published on Docker Hub anymore. Please migrate to `ghcr.io/metal-stack/builder` in case you are using the image from Docker Hub.

[Gerrit91]

This would remove the push to docker.io.

@majst01 Can we drop the push to this location? I think nobody should use really depend on it as there's ghcr.io option.

[majst01]

This would remove the push to docker.io.

@majst01 Can we drop the push to this location? I think nobody should use really depend on it as there's ghcr.io option.

Should, but who knows ? Maybe we can see at docker.io when the last pull happened

[Gerrit91]

I don't have the access to our Docker Hub account. 😓

[Gerrit91]

We can also just write it to the release notes and that's it. It can only build development builds for people and even then they only do not receive any more updates.

[Gerrit91]

I added a NOTEWORTHY section that people should use the image from ghcr.io instead. So from my side this one is good to go.