feat: add role management helper methods

[Beesh1]

Summary

Adds helper methods for managing user role assignments through the Casdoor role API, following the workflow described in issue #4360.

Changes

New Methods:

• get_roles() - Retrieve all roles in the organization
• get_role(role_name) - Retrieve a specific role
• update_role(role) - Update role configuration
• assign_role_to_user(username, role_name) - Add user to role
• remove_role_from_user(username, role_name) - Remove user from role
• get_user_roles(username) - List all roles for a user

All methods available in both sync (CasdoorSDK) and async (AsyncCasdoorSDK) versions.

Implementation

These methods handle role assignment through the proper API workflow:

1. Fetch the target role via get-role endpoint
2. Modify the role's users array
3. Update the role via update-role endpoint

This approach correctly manages the extended roles field as outlined in the maintainer response to #4360.

Usage Example

from casdoor import CasdoorSDK

sdk = CasdoorSDK(
    endpoint="https://door.example.com",
    client_id="your_client_id",
    client_secret="your_client_secret",
    certificate="",
    org_name="your_org",
    application_name="your_app"
)

# Assign role
sdk.assign_role_to_user('john', 'admin')

# Verify assignment
roles = sdk.get_user_roles('john')

# Remove role
sdk.remove_role_from_user('john', 'admin')

Testing

Validated against production Casdoor instance with real role assignments and removals.

Related

Implements the solution discussed in #4360.

[Beesh1]

@hsluoyz this provides an easy solution using the SDK

[github-actions]

🎉 This PR is included in version 1.40.0 🎉

The release is available on:

• v1.40.0
• GitHub release

Your semantic-release bot 📦🚀