Add IAM permissions and roles documentation

[phantomii]

Document permission structure (service.resource.action), wildcard usage, and deny-by-default security model. Explain role and permission bindings, project-scoped access, and token introspection flow. Include API examples for creating permissions, roles, and bindings. Add service integration guide with Python code examples for permission checks and middleware. Cover best practices, error handling, and important notes on caching and access control.

[gemini-code-assist]

Code Review

This pull request introduces a comprehensive documentation guide for the Identity and Access Management (IAM) system, covering permission structures, role bindings, and project-scoped access, along with Python code templates for service integration. The review feedback identifies several improvements for the provided code examples, including correcting an API endpoint URL, implementing wildcard support for permission validation, following Python best practices for decorators using functools.wraps, and adding robust error handling in the authentication middleware.