register_external_observer: Register an external MLflow observer
In mrkaye97/lightMLFlow: A lightweight R wrapper for the MLFlow REST API

Registers an external MLflow observer that will receive a register_tracking_event(event_name, data) callback on any model tracking event such as "create_run", "delete_run", or "log_metric". Each observer should have a register_tracking_event(event_name, data) callback accepting a character vector event_name specifying the name of the tracking event, and data containing a list of attributes of the event. The callback should be non-blocking, and ideally should complete instantaneously. Any exception thrown from the callback will be ignored.