change: Model interface loading

[mathysgrapotte]

Is your change request related to a problem? Please describe.

Current interface loading in utils/launch_utils.py loads a model from file if the class is named Model. This lacks flexibility.

Describe the solution you'd like

Have a register decorator would be best :

# In model files
from stimulus import register_model

@register_model
class ModelTitanic(...):
    ...

we could then validate the interface using a small validation method :

def validate_model_interface(cls):
    required_methods = ['forward', 'compute_loss', 'batch']
    for method in required_methods:
        if not hasattr(cls, method):
            raise ModelInterfaceError(f"Model {cls.__name__} missing {method}")