The idea is to make easier to start developing with guillotina and a frontend. Right now guillotina returns a 401 (Unauthorized) when origin is not allowed, and because this is returned from a OPTIONS it's not possible to provide a nice message to distinguish the cors error from a authentication error.
I think most frameworks doesn't have CORS enabled by default and probably the CORS would be managed by a reverse proxy when guillotina is deployed in production, so I think making this opt-in would be better.
What do you think?