Clarify `authorization_service` in Authentication Documentation

[Ckk3]

In our documentation for authentication in docs/guides/authentication.md, there's a reference to an authorization_service that's not defined or explained:

We received some feedbacks were some people don't understand what authorization_service is or where it comes from.

What can we do to make it better?

This is some thoughts I had

• Add a clear comment indicating that this is a placeholder for custom auth logic?

# This would be your custom authorization service that validates tokens
# and returns user objects. It's not provided by Strawberry.
return authorization_service.authorize(authorization)

• Should we add more comprehensive authentication examples (e.g., with JWT)?
• Would it be useful to have a complete authentication example?

Feedbacks