Mixed Bean Salad

1/2 pound green beans, trimmed and halved crosswise
 2 tablespoons cider vinegar
 3 tablespoons extra-virgin olive oil
 1 tablespoon fresh oregano leaves, finely chopped
 1 tablespoon fresh parsley leaves, finely chopped
 1 shallot, thinly sliced
 2 teaspoons grainy mustard
 1 can (15.5 ounces) red kidney beans, rinsed and drained
 1 can (15.5 ounces) chickpeas, rinsed and drained
  Coarse salt and ground pepper
 
In a large pot of boiling salted water, cook green beans until bright green and crisp-tender, 2 to 3 minutes. Drain and rinse under cold water until cool. In a large bowl, whisk together vinegar, oil, oregano, shallot, and mustard. Add green beans, red kidney beans, and chickpeas; toss well to combine. Season with salt and pepper.