User Authentication and Flow Run Attribution in Prefect

[aaazzam]

With the introduction of basic authentication in Prefect 3.1.8+, there's an emerging need to discuss best practices around user authentication and flow run attribution. While the core basic auth functionality works as designed, some users are looking to implement more sophisticated authentication patterns, particularly around tracking which users are executing specific flows. This discussion aims to explore potential approaches for implementing user tracking in Prefect, including:

The interaction between reverse proxy authentication and Prefect's built-in basic auth
Methods for passing user information from the authentication layer to flow runs
Best practices for implementing user attribution in enterprise deployments

Let's discuss potential solutions and share experiences implementing authentication in Prefect deployments.

inspired by #16555 by @larandvit