streamline process_parameters

[mikarubi]

Remove redundant validation of parameters from process_parameters (after #31 is merged) because this validation now occurs in parameter_models

[luiztauffer]

as of now, if a parameters file (json) already exists, the default behavior is to load from it.
should we have an optional flag, e.g. overwrite: bool = False, that allows the user to overwrite the local file with a new processed parameters dict?

[mikarubi]

No, the current setup is good. The idea is that once a parameter file is created, it should not be overwritten.