[Feature]: New endpoints to return structured taxonomy

[akijakya]

Problem Statement

The OASF SDK among others would make great use of endpoints that return the taxonomy of the class families in a nested structure so the hierarchy can be parsed without extra logic with discovering parent and children classes. The current module/skill/domain_categories endpoint only structures classes under their categories but the classes list is flat - similar to the response of the modules/skills/domains API endpoints.

Proposed Solution

Create a new taxonomy group of endpoints for the class families that returns id, (hierarchical) name, caption, description of every class in a nested json, which can be used to discover classes by LLMs via the directory's MCP server that uses OASF SDK leveraging this new endpoint.

Alternatives Considered

No response

Additional Context

No response

Checklist

• I have read the contributing guidelines.
• I have verified this does not duplicate an existing feature request.