[JAVA] Generate client files with multiple enum `oneOf` types (!12687) · Merge requests · OpenAPI Tools / openapi-generator

Created by: l3ender

This change adds support for generating client files from multiple oneOf included items in an API definition. See https://github.com/OpenAPITools/openapi-generator/issues/12545 for full description/detail.

I'm unsure if https://github.com/OpenAPITools/openapi-generator/commit/6b9f985331613b0c23e4bd4862b1b33d641a6b14 is appropriate, but the files were changed after running ./bin/generate-samples.sh. So in following the PR template, I have committed the changes!

Read the contribution guidelines.
Pull Request title clearly describes the work in the pull request and Pull Request description provides details about how to validate the work. Missing information here may result in delayed response from the community.
Run the following to build the project and update samples:
```
./mvnw clean package 
./bin/generate-samples.sh
./bin/utils/export_docs_generators.sh
```
Commit all changed files. This is important, as CI jobs will verify all generator outputs of your HEAD commit as it would merge with master. These must match the expectations made by your contribution. You may regenerate an individual generator by passing the relevant config(s) as an argument to the script, for example ./bin/generate-samples.sh bin/configs/java*. For Windows users, please run the script in Git BASH.
File the PR against the correct branch: master (6.0.1) (patch release), 6.1.x (breaking changes with fallbacks), 7.0.x (breaking changes without fallbacks)
If your PR is targeting a particular programming language, @mention the technical committee members, so they are more likely to review the pull request.

@bbdouglas @sreeshas @jfiala @lukoyanov @cbornet @jeff9finger @karismann @Zomzog @lwlee2608

Thank you!