[New Feature] Experiment with removing the Airflow authentication altogether

[LucaCinquini]

Working in a separate branch, figure out what it would take to remove the login from Airflow. This would be useful in case we decide that all Cognito authentication should be taken care by the top level proxy.

[LucaCinquini]

See PR #244 for implementation details. Removing the Airflow front-end authentication is possible, the next step is to test the flow when a user hits the top-level proxy URL and has to login with Cognito.

[LucaCinquini]

This feature was successfully demonstrated, but it remains unmerged until we can fully use Cognito at the service-level proxy for A&A both with the User Interface and the Airflow and OGC APIs.