fix(BA-2832): Seperate permission group DTOs based on whether relationship data load is needed

[seedspirit]

resolves #6414 (BA-2832)

Checklist: (if applicable)

• Milestone metadata specifying the target backport version
• Mention to the original issue
• Installer updates including:
  • Fixtures for db schema changes
  • New mandatory config options
• Update of end-to-end CLI integration tests in ai.backend.test
• API server-client counterparts (e.g., manager API -> client SDK)
• Test case(s) to:
  • Demonstrate the difference of before/after
  • Demonstrate the flow of abstract/conceptual models with a concrete implementation
• Documentation
  • Contents in the docs directory
  • docstrings in public interfaces and type annotations

[Copilot]

Pull Request Overview

This PR refactors permission group DTOs to separate concerns between basic data transfer and extended data that includes relationship data. The change introduces PermissionGroupExtendedData as a new DTO that includes nested permissions, while keeping PermissionGroupData as a lighter-weight alternative without relationships. This separation prevents lazy loading errors by making relationship data requirements explicit at the type level.

Key changes:

• Introduced PermissionGroupExtendedData DTO to include nested permissions data
• Updated RoleDataWithPermissions to use PermissionGroupExtendedData instead of PermissionGroupData
• Added to_extended_data() method to PermissionGroupRow model for converting to the extended DTO

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/ai/backend/manager/data/permission/permission_group.py	Adds new PermissionGroupExtendedData dataclass with permissions field
src/ai/backend/manager/models/rbac_models/permission/permission_group.py	Implements to_extended_data() method and imports new DTO
src/ai/backend/manager/data/permission/role.py	Updates import and type annotation to use PermissionGroupExtendedData
src/ai/backend/manager/models/rbac_models/role.py	Changes method call from to_data() to to_extended_data()
changes/6451.enhance.md	Documents the enhancement

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[fregataa]

Good. How about setting PR prefix as fix rather than refactor?