Event listeners for DAG processing events

[numice]

Description
I'd like to see if it's a good idea to have an event listener for Dag Processing events, for example, when a new or modified dag is loaded in the dag bag. Right now, I can see only events when a dag state changes or a task instance state changes but I don't see an event when a dag is loaded.

Use case/motivation
In my use case, I'm planning to add some metadata to a dag file and read it when the dag is loaded and then run a small function like monkeypatching the dag depending on the metadata.

There's a PEP https://peps.python.org/pep-0723/ to one suggestion to embed a script inside a python file and I'd like to read this when a dag is processed and parsed.

So right now what I can think of is scanning the whole repo and parse the files, which could maybe be done by a running dag, but since Airflow is already processing new dags so I think it might be a better idea to have these event listeners and implementing event handlers.