Slow-Cooker Pulled Turkey Sandwiches

Name: Slow-Cooker Pulled Turkey Sandwiches
Yield: 4-6
Ingredients: 4 Turkey thighs (about 4 pounds); 1 Red onion, small; 1/2 cup Ketchup; 2 tbsp Mustard, yellow; 1/4 cup Brown sugar, packed light; 1 tbsp Chili powder; 1 Kosher salt and freshly ground black pepper; 1 tbsp Apple cider vinegar; 1 tsp Cumin, ground