[BUG] [JAVA] [MVN] maven plugin won't copy files in src/main/resources when addCompileSourceRoot is set

Description

When java generator is used with a the maven plugin, and addCompileSourceRoot is set, the generated source directory (target/generated-sources/.../src/main/java) is added as a project source directory, but the generated resource directory (target/generated-sources/.../src/main/resources) is ignored.

This will make all files generated at target/.../src/main/java to get compiled and placed in the target/classes directory (the desired outcome), but the files that are generated at target/.../src/main/resources will get ignored, and won't be found in the target/classes file (which is not the desired outcome) - so the final JAR file will miss these files.

openapi-generator version

6.6.0 and 7.0.0-SNAPSHOT

Generation Details

java (or other jvm based generator), used by the maven plugin. Specifically reproduced with the java + native generator.

Steps to reproduce

Run the following pom file (mvn clean compile):
https://gist.github.com/yonatang/04150af8e0d4d3eef2c779173a441abb

The target/generated-sources/openapi/src/main/resources will have a file named openapi/openapi.yaml file, but that file will
be missing from the target/classes folder.
The expected behavior is to see in target/classes a file named openapi/openapi.yaml file.

Related issues/PRs

Couldn't fine any.

Suggest a fix

In this method at the Maven's CodeGenMojo class, the project.addResource() should be invoked as well.

The fix should be straight forward for most cases (when using the default source folder - src/main/java), but the main challenge is to handle cases where a non-default sourceFolder was defined - the java generator doesn't have a resourceFolder option and therefore it is unclear what is the actual resource folder. Notice that src/main/resource even seems to be hardcoded in some cases in JavaClientCodegen.

I think this issue calls out a flaw in the design about resources for java based plugins - you can configure the sources directory but can't configure the resources directory.

Start in modules/openapi-generator-maven-plugin/src/main/java/org/openapitools/codegen/plugin/CodeGenMojo.java at the referenced method, then inspect JavaClientCodegen.java around the hardcoded resource path. Reproduce with the linked POM and mvn clean compile; done means generated files under src/main/resources, including openapi/openapi.yaml, appear in target/classes for default and non-default sourceFolder cases.