Invert config dependencies

[girotobial]

Add present, every module imports the config module. In turn the config module imports other modules, and then, runs code that imports the config file and changes local variables in the modules it imported. This makes testing more difficult as now most modules are dependant on the configuration file being loaded and tested correctly.

I propose that config should be held in a Config class which has sensible defaults and validates read values. With functions in the config module for reading and writing to file.

Something like

@dataclass
class Config:
    verbosity: int = 1
    cleaning_level: int = 1
    skip_downlodas: bool = False


def read_config(file_path: Optional[Union[Path, str]] = DEFAULT_CONFIG_FILEPATH) -> Config:
    ...

def write_config(config: Config, file_path: Union[Path, str]) -> None:
    ...

The Config class can then be imported and used in tests, but read from file and loaded at run time.