Add m2e lifecycle metadata for maven-dependency-plugin

[kwin]

This closes #1077

[github-actions]

Test Results

606 tests  ±0   599 ✔️ ±0   8m 34s ⏱️ - 1m 15s
  97 suites ±0       7 💤 ±0 
  97 files   ±0       0 ❌ ±0 

Results for commit dbfe0c1. ± Comparison against base commit 9f3ad47.

[HannesWell]

Thanks @kwin for this update. Your dedication to spread the BuildContextAPI is really helpful!

Do you plan to have a release of the maven-dependency-plugin soon?
Because otherwise users get warnings telling them they should update the dependency-plugin but that update is not available.
So if the 3.4 release will take some more time I suggest to at least remove the warning until then.

[kwin]

The release should happen soon: https://lists.apache.org/thread/xo0m4dztj0v67rdv4n843ls3dxny66xg

[HannesWell]

Great. 👍🏽

[laeubi]

I'm not sure if an error is appropriate here, why not a warning instead? I assume even with a release there will be some projects that do not update immediately and some older projects that probably never update so all will get an error marker now the user will not really be able to act upon.

[kwin]

The behaviour should be the same for all Maven plugins, and the existing ones emit an error already (https://github.com/kwin/m2e-core/blob/dbfe0c1fc2538694edc66a61fa404073b5cffd3b/org.eclipse.m2e.core/lifecycle-mapping-metadata.xml#L116). But I agree that most probably all should be changed to a warning.

[laeubi]

A while back we changed missing mappings from error > warning so I think this would be applicable also.

Error seems really disturbing to the user given that the only harm that could happen is that nothing happens...

[HannesWell]

Yes the behavior should be the same and yes warning should be enough.
But the enum PluginExecutionAction only has the values ignore, execute, configurator and error, which are effectively the supported children of an action element. So we have to add a warning element to support that.

The relevant code to adjust this is probably LifecycleMappingFactory.instantiateProjectConfigurators().

That being said, I did not manage to actually get the warning in the Editor. I only got Plugin execution not covered warnings...

[laeubi]

I can't think of a use-case where error is anything useful, why should I error the user about my mojo in an IDE? So probably the "error" can just be treated as a warning marker...