Slow Cooker Everything Bagel Breakfast Casserole

Name: Slow Cooker Everything Bagel Breakfast Casserole
Ingredients: Nonstick baking spray; 8 ounces breakfast sausage, casing removed; 8 large eggs; 2 cups whole milk; 1 3/4 cups half-and-half; Pinch cayenne; Kosher salt and freshly ground black pepper; 3 large plain bagels (about 4 ounces each), split and cut into 1-inch pieces; 8 ounces cream cheese, cut into 1/2-inch cubes; 1 red bell pepper, finely diced; 1 cup (about 4 ounces) shredded medium provolone; 2 tablespoons everything bagel seasoning; 2 scallions, thinly sliced