feat(parser): add support for type definitions in schema and enhance code generation for DTOs across Rust, Python, and TypeScript

[sophatvathana]

Summary

• feat(parser): add support for type definitions in schema and enhance code generation for DTOs across Rust, Python, and TypeScript

Changes

• rohas-codegen

Testing

• cargo test
• cargo fmt --check
• Other (describe):

Checklist

• I updated relevant docs (README, CONTRIBUTING, etc.).
• I added tests or explained why they’re unnecessary.
• I verified CI passes locally or explained why it wasn’t run.

Screenshots / Notes (optional)

• Add screenshots, logs, or anything reviewers should see.