Upon successful creating of release packages and testing their correctness, packages should be published so they can be installed and used.
Publishing step includes:
* marking the source code versions released ("tagging" in git vocabulary)
* publishing tarball/zip artifacts to a defined repository
* publishing Docker image artifacts to a defined repository
* adding additional metadata ("tags") to published artifacts
For completeness, the initial release pipeline should also use the publishing step, even though the actual publishing is not going to happening yet, pending the decision on where to publish the release artifacts.
In other words, the publishing step will be to a significant degree a "placeholder" only for now. The actual publishing-related commands will be replaced by the placeholder commands (e.g. `echo "Tagging Wikibase commit abc123 as XYZ"`, `echo "Publishing Wikibase tarball XYZ-123.tar.gz to ABC"`).
**Acceptance criteria**
[] "Publish" step is defined for both tarball and container image "pipelines", with placeholder commands run for the time being
[] Open questions and other details that need to be specified for the "production" "release pipeline" have been collected and submitted as a comment on this task