Option to disable service authentication

## Description
I’d like to request a feature that allows disabling the authentication mechanism on user services (particularly IDEs like VSCode, etc.).

## Use case
We are deploying an external reverse proxy that handles authentication using the same Identity Provider as Onyxia. This proxy will be in front of all services, ensuring that access is securely managed. However, the built-in authentication of each individual service becomes redundant.

## Solution
- Introduce a configuration option to disable the service-level authentication for spawned services ;
- Add on services catalogs possibility to disable password authentication ;

Thanks!