In a large bowl, combine vinegar, mustard, 1/4 tsp. salt and 1/8 tsp. pepper. Whisk until salt has dissolved. Slowly whisk in olive oil until incorporated. Add tuna, chopped chickpeas, roasted peppers and olives to bowl and stir until well combined. Taste and season with additional salt and pepper, if desired. Cover and chill until ready to pack. Serve salad over greens or on bread or crackers, if desired.