Melt butter or margarine in a skillet over medium heat. Cook onion, celery, carrots, and parsley in butter, stirring frequently. Cook sausage in a separate skillet thoroughly until crumbled. Beat eggs in separate bowl. Spoon cooked vegetables over bread cubes in a very large mixing bowl. Mix well. Add sausage, then cranberries. Season mixture with poultry seasoning, salt, and pepper. Pour in enough broth to moisten, about 2 cups and mix in eggs. Transfer mixture to slow cooker, pour another 1/2 cup broth and cover. Cook on High for 45 minutes, then reduce heat to Low, and cook for 4 to 6 hours. Add broth as needed to keep moistened.