feat: #3697 add waypoints external resources section

[florentcadot]

#3697

Associated backend PR: c2corg/v6_api#1747

How to test:

Pull the associated backend branch feature/add-waypoints-external-resources
Run the added migration using docker-compose exec api .build/venv/bin/alembic upgrade head

Create a new waypoint and fill the external_resources field. Then update the external resources of this.

You should see something like this:

[brunobesson]

It looks good to me thanks. I haven't tested it though because I couldn't manage to launch the API side on my laptop (work restrictions + I am not fluent with python).

IMHO, we can merge both parts (backend and frontend).