Resolve "Enable data model pipeline for main branch to publish jar files."

Related issues

Enable data model pipeline for main branch to publish jar file in gitlab registry.

Acceptance criteria

• Implemented code changes don't diverge from the related issue.
• Documentation reflects the status quo after merge.
• Only released versions of dependencies are used (i.e. no snapshot versions).
• Pipeline still works.
• GitLab issue is up-to-date.

If necessary, the following sections have been updated:

• Readme.md
• Documentation

Proposed squash commit message

Enable data model pipeline for main branche to publish jar file in gitlab registry.

• Remove workflow rule to run only in merge requests.
• This was a bug as only for the main branch jar files are published to the gitlab registry.

Closes #19 (closed)