Provide fix suggestions for not covered Maven plugin execution in project build lifecycle

[testforstephen]

Signed-off-by: Jinbo Wang jinbwan@microsoft.com

This PR requires the side PR at eclipse-jdtls/eclipse.jdt.ls#1770. It's used to mitigate the issues at #177, #566, #935 and #1910.

Here are the main things this PR added.

• Change the default value of preference "java.configuration.maven.notCoveredPluginExecutionSeverity" to "error", and show error diagnostics to user for awareness.
• Provide quickfix suggestions for not covered Maven plugin execution in pom.xml.

[testforstephen]

See a sample project https://github.com/antlr/stringtemplate4 to try this PR.
See a demo about the UX.

notCoveredExecution.mov

A follow-up improvement is to "discover new m2e connectors". Eclipse provides such a quick fix when reporting "not covered execution" error in Maven project. Looks like it's based on the catalog https://repo1.maven.org/maven2/.m2e/discovery-catalog/connectors.xml for discovery. Need more evaluation on the cost to support discovering and installing m2e connector in VS Code, will take it as a future improvement.

// @fbricon Could you help review the solution? thanks.

[fbricon]

I guess it will help in some cases, but I'm afraid we're opening a can of worms with the whole m2e connector thing (especially the discovery mechanism).

The best thing is still for maven plugins authors to provide native support for m2e. The doc should probably encourage users to request such integration directly from these projects.

[testforstephen]

Yes, the m2e connectors are a bit too complex and not planned to add them to VS Code. We are currently just providing some suggestions for common workarounds, and also stating in the doc that the best approach would be to make the Maven plugin directly compatible with m2e.

[testforstephen]

Update:

• The latest commit has changed the default severity level to "warning".
• The PI didn't break the deployment to maven central.
  Tried deploying a pom with PI <?m2e execute onConfiguration?> to oss.sonatype.org, it worked. And reference the sample dependency in other maven project, no issues were found.

[rgrunber]

I will look at this today.

[rgrunber]

Seems to be working well. Just a few corner cases to consider.

[rgrunber]

LGTM. Feel free to merge when ready. I would probably squash the commits first.