Curried Chicken Salad With Grapes

Name: Curried Chicken Salad With Grapes
Ingredients: 1 large onion, chopped; 2 tablespoons olive oil; 2 tablespoons curry powder (preferably Madras); 1/2 cup tomato juice; 1/2 cup dry red wine; 2 tablespoons chutney; 1 2- to 2 1/2-pound rotisserie chicken, meat cut into 1-inch pieces; 3 stalks celery, chopped (about 1 1/2 cups); 1 small red onion, chopped (about 1/2 cup); 3/4 cup mayonnaise; kosher salt and black pepper; 1 medium bunch seedless green grapes, halved (about 1 1/2 cups); 1 10-ounce bag baby spinach leaves