Bring a saucepan of two cups salted water to boil. Add couscous, stir, cover and reduce the heat to medium. Cook until all the liquid is absorbed, for about 10 minutes. Fluff with a fork and transfer to a bowl to cool. Prepare the dressing for the salad by whisking together the olive oil, lemon juice, garlic clove and Dijon mustard. Stir to combine, and then pour over the cooled couscous. Add the cucumbers, tomatoes, chickpeas, feta cheese, pine nuts, parsley and mint on top, and toss gently to combine.