Slow Cooker Smoked Sausage and Sauerkraut Soup

1 lb smoked sausage, sliced 5 cups chicken stock 1 lb sauerkraut, drained 2 cups fresh mushrooms, sliced 2 large carrots, diced 3 stalks celery, sliced 3 medium red potatoes, diced 1 medium sweet onion, finely diced 1 can diced tomatoes 2 teaspoons dried dill 1 pinch caraway seeds, (optional) 6 strips bacon, cooked crisp and crumbled (optional) 1/3 cup Parmesan cheese, finely grated (optional)