fix: Make GraalVmProcessor Arguments Optional

[ppkarwasz]

Fixes #3771

This PR makes the -Alog4j.graalvm.groupId and -Alog4j.graalvm.artifactId arguments optional.

• If no arguments are provided, metadata is stored in:

  META-INF/native-image/log4j-generated/<content-derived-value>
  

  Previously an error was thrown.

• If arguments are provided, files go to:

  META-INF/native-image/log4j-generated/<groupId>/<artifactId>
  

  Previously META-INF/native-image/<groupId>/<artifactId> was used. The new path prevents collisions with user-provided metadata.

[Copilot]

Pull Request Overview

This PR makes the GraalVM metadata processor arguments optional, updates the default storage path to include a log4j-generated prefix, and refactors how reflect-config JSON is generated and emitted.

• Changed GraalVmProcessor to compute reflect-config once into a byte array and derive a fallback folder name via a hash.
• Updated getReachabilityMetadataPath to return a warning (not error) and use the new META-INF/native-image/log4j-generated hierarchy.
• Expanded tests to cover new path logic, warning emission, and metadata contents.

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

File	Description
src/changelog/.2.x.x/3771_graalvm-params.xml	Added changelog entry for optional GraalVM args
GraalVmProcessor.java	Made processor arguments optional, added byte-buffered metadata, new path logic, and warning for missing options
FakePlugin.java / FakeAnnotations.java	Added test fixtures for plugins and annotation visitors
GraalVmProcessorTest.java	Refactored test helper, added parameterized path tests and warning check

Comments suppressed due to low confidence (2)

log4j-core/src/main/java/org/apache/logging/log4j/core/config/plugins/processor/GraalVmProcessor.java:229

• [nitpick] Consider adding a JavaDoc comment for this overloaded getReachabilityMetadataPath method to explain the fallbackFolderName parameter and how the fallback hash is computed, improving maintainability for future readers.

    String getReachabilityMetadataPath(

log4j-core/src/main/java/org/apache/logging/log4j/core/config/plugins/processor/GraalVmProcessor.java:230

• The use of the @Nullable annotation requires an import (e.g., org.jspecify.annotations.Nullable or javax.annotation.Nullable), but no such import is present. Add the correct import to avoid a compile error.

            @Nullable String groupId, @Nullable String artifactId, String fallbackFolderName) {