Optuna + Hydra ?

Hey @jinglada @jmichel

There is a hydra plugin available to define optuna hyperparameters from the hydra config, it might be beneficial for experiments if we could keep track of sweeps, etc. in an automated manner, what do you think ? (@sanchezvvictor and I would like to start experimenting on AutoEncoding first to then focus on both diffusion and variational variants)