feat: publish Groovydoc Enhancer Plugin for use in end-user Grails apps

[jamesfredley]

Summary

Potential path to allow end-user Grails applications to use modern Java features (17+) and still generate accurate Groovydoc documentation.

Gradle's built-in Groovydoc task does not expose the javaVersion parameter (added in Groovy 4.0.27 via GROOVY-11668), so projects using Java 17+ features (sealed classes, records, pattern matching, text blocks, etc.) fail to generate Groovydoc. This PR publishes the GroovydocEnhancerPlugin (from #15420) as a standalone Gradle plugin that end-user Grails applications can consume.

Changes

New Published Module: grails-gradle-groovydoc

• Maven coordinate: org.apache.grails.gradle:grails-gradle-groovydoc
• Plugin ID: org.apache.grails.gradle.groovydoc
• Located in grails-gradle/groovydoc/ following the existing grails-gradle subproject pattern
• Automatically included in grails-gradle-bom (subproject auto-inclusion)
• Manually added to grails-bom via gradleBuildProjects map for end-user app BOM resolution

Forge Integration (DefaultFeature)

• New GroovydocEnhancer feature class applied to all generated Grails applications by default
• Adds grails-gradle-groovydoc as a buildscript classpath dependency (version managed by grails-bom)
• Applies org.apache.grails.gradle.groovydoc plugin via apply plugin

Profile Integration

• Updated base/profile.yml to include the plugin for grails CLI-based app generation
• Both forge and profile paths now generate apps with Groovydoc enhancer support

Build-Logic

• build-logic/ retains its own copy of the plugin for the framework build itself (bootstrap constraint - build-logic cannot depend on grails-gradle artifacts without circular dependency)
• The published grails-gradle-groovydoc module is the canonical version for end-user consumption

Architecture Note

There are two copies of the enhancer plugin:

1. build-logic/plugins/ - convention plugin for building grails-core itself (unpublished, internal)
2. grails-gradle/groovydoc/ - published plugin for end-user Grails apps

This duplication exists because build-logic is evaluated before grails-gradle builds, creating a bootstrap dependency that prevents build-logic from consuming the published artifact directly. Future work could explore composite build substitution or a shared source set to eliminate this duplication.

Testing

• grails-gradle-groovydoc builds successfully standalone
• grails-bom POM generation succeeds with the new artifact
• grails-forge-core compiles with the new feature class
• Code style checks pass

Depends On

• Adopt AntBuilder groovydoc with javaVersion support #15420

[jamesfredley]

A Third "commons" build appears to be the only way to remove the duplication.

[jamesfredley]

Or moving it to a separate repo, as we have done with publishing.

[jdaugherty]

In order to publish this, its going to have to go to a separate repository...

[jamesfredley]

@jdaugherty I will add that to agenda for the meeting, next week.