Simplify site generation

[vy]

Warning! These changes are based on the work delivered in #1145 replacing the maven-changes-plugin. Hence, that PR needs to be merged first!

This PR attempts to simplify the site generation.
Highlights from the changes are as follows:

1. all Maven reporting is disabled
2. Coveralls, JaCoCo, DOAP, PDF configurations are removed
3. enforce-upper-bound-deps Maven enforcer rule is fixed
4. /pom.xml is overhauled (developers are simplified, contributors are removed, unused configurations/properties are removed, etc.)
5. maven-site-plugin is disabled for all modules except /pom.xml
6. all <module>/src/site/markdown/index.md[.vm] files are moved to /src/site/markdown/<module>.md[.vm]
7. build instructions are updated

As a result, ./mvnw site takes less than 30s on a decent laptop.

[rgoers]

I pulled logging-log4j-tools and built it. I ran mvn clean install (which worked). I then ran mvn site, which failed with

[ERROR] Failed to execute goal org.apache.maven.plugins:maven-site-plugin:3.12.0:site (default-site) on project log4j: SiteToolException: The site descriptor cannot be resolved from the repository: ArtifactResolutionException: Unable to locate site descriptor: Could not transfer artifact org.apache.logging:logging-parent:xml:site_en:7 from/to spring-snapshots (https://repo.spring.io/libs-snapshot-local): Failed to transfer file https://repo.spring.io/libs-snapshot-local/org/apache/logging/logging-parent/7/logging-parent-7-site_en.xml with status code 409
[ERROR]   org.apache.logging:logging-parent:xml:7

[vy]

@rgoers, it simply works on my machine. Since logging-log4j-tools release is stuck on INFRA-23996, I cannot prove my claim in CI, i.e., GitHub Actions.

Would you mind trying ./mvnw clean site in mvn-site-simplified branch, please?

Which module fails to build? log4j-spring-cloud-config-sample-server?

[rgoers]

It fails at the root of the project. It isn't in any module.

[ppkarwasz]

@rgoers: my guess is that you are using a Maven Central mirror that does not contain the logging-parent.site.* artifacts?

[rgoers]

It turns out I had some Spring repos in my settings.xml from when I was adding out stuff to Spring and that messed it up. After removing it the site built fine and only took 47 seconds!

However, I still have to look at the results.

[rgoers]

Under components, when I select "Implementation" I get a file not found. All the other pages are fine.

Note - make sure you do mvn site:stage -DstagingDirectory=$HOME/log4j to generate the full web site.

[vy]

Under components, when I select "Implementation" I get a file not found. All the other pages are fine.

I have removed that page, since it was empty anyway. Now, in c612522, removed it from the menu too.

Note - make sure you do mvn site:stage -DstagingDirectory=$HOME/log4j to generate the full web site.

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