Optionally rate artifact-reference-checker:unify check as warning

[kaklakariada]

PJ reported a use case in which the developer didn't plan to do a release immediately (for example when updating CI files) but bump the version in the .pom file so the current documentation file for the current changes (changelog) doesn't get overwritten.

After that PK forces to update the documentation references to this future version, thus referencing a yet unreleased version.

Problem

References to a yet unreleased version might be confusing or wrong towards customers.

Proposed mitigation

Reference checker should check if the release date in the latest changelog file is defined or not:

• If the changelog contains a concrete date (e.g. # Project Keeper 2.9.16, released 2023-11-13), work as normal
• If the changelog contains a dummy date (e.g. # Project Keeper 2.9.16, released 2023-??-??), reference checker logs a warning and does nothing

[pj-spoelders]

Thanks chipi! I like the proposed solution

[pj-spoelders]

Another idea is to add a flag/option that can be set for the maven plugin in the configuration section, like it's done here: spotify/fmt-maven-plugin#153
At the moment to run project-keeper:fix when there's already a release of the current version you have to increase the version already. This is also not ideal but I guess this won't change. TBD'd.

[redcatbear]

People, please keep unreleased changes to a acceptable minimum, then we can live with the inconsistency. I am going to close this ticket. I understand where it comes from, but there are so many things that have priority over this issue.