RESTWS-980: Initial implementation of OpenAPI Generator Maven Plugin with JavaParser integration

[capernix]

Description of what I changed

Introduced a new OpenAPI Generator Maven Plugin that integrates JavaParser to extract Javadoc from OpenMRS REST resource classes. This initial implementation serves as a proof-of-concept for enhancing OpenAPI documentation with descriptive information from source code.

Key Implementation Details:

1. Created a custom Maven plugin (openapi-generator-maven-plugin) with JavaParser integration
2. Implemented source file location logic to find Java classes across module source roots
3. Added functionality to parse Java source files and extract class-level Javadoc comments
4. Successfully tested extraction of Javadoc from PatientResource1_8 class
5. Fixed a Maven build dependency issue by moving the unpack-dependencies goal from generate-resources to prepare-package phase

This implementation provides the foundation for programmatically enhancing API documentation by leveraging the existing Javadoc in the codebase.

PS: I also pushed the code for the schema introspector alongside so the work can be combined in future commits.

Issue I worked on

https://openmrs.atlassian.net/browse/RESTWS-980

Checklist: I completed these to help reviewers :)

• [x] My IDE is configured to follow the code style of this project.

  No? Unsure? -> configure your IDE, format the code and add the changes with git add . && git commit --amend

• [] I have added tests to cover my changes. (If you refactored
  existing code that was well tested you do not have to add tests)

  No? -> write tests and add them to this commit git add . && git commit --amend

• [x] I ran mvn clean package right before creating this pull request and
  added all formatting changes to my commit.

  No? -> execute above command

• [x] All new and existing tests passed.

  No? -> figure out why and add the fix to your commit. It is your responsibility to make sure your code works.

• [x] My pull request is based on the latest changes of the master branch.

  No? Unsure? -> execute command git pull --rebase upstream master