Move FABs base Security Manager into Airflow.

[jhtimmins]

As one of the first steps in refactoring Airflow's usage of the FAB security manager, copy FAB's base SecurityManager classes into Airflow.

[uranusjr]

Do we want to keep FAB in the name? If we end up removing Rlask-Appbuilder altogether, the name reference may feel confusing to newcomers.

[jhtimmins]

Do we want to keep FAB in the name? If we end up removing Flask-Appbuilder altogether, the name reference may feel confusing to newcomers.

@uranusjr I'm refactoring it in pieces, so I plan to change the naming in a PR that's coming shortly. For now though, it exactly matches the FAB architecture and references FAB models/concepts.

[uranusjr]

I see, thanks for the clarification.

[github-actions]

This pull request has been automatically marked as stale because it has not had recent activity. It will be closed in 5 days if no further activity occurs. Thank you for your contributions.

[github-actions]

The PR most likely needs to run full matrix of tests because it modifies parts of the core of Airflow. However, committers might decide to merge it quickly and take the risk. If they don't merge it quickly - please rebase it to the latest main at your convenience, or amend the last commit of the PR, and push it with --force-with-lease.