Pork Wellington with Greens and Grapes

Name: Pork Wellington with Greens and Grapes
Ingredients: Kosher salt and freshly ground pepper; 1 large pork tenderloin (about 1 1/2 pounds), trimmed; 1 8-ounce tube refrigerated crescent dough; 2 ounces Gruyere cheese, thinly sliced; 1/2 small shallot, finely chopped; 1 tablespoon white wine vinegar; 1 5-ounce package mixed baby greens (about 8 cups); 3/4 cup seedless grapes, halved; 1/4 cup extra-virgin olive oil; 1 1/2 tablespoons whole-grain mustard; 2 teaspoons chopped mixed fresh herbs (such as thyme, parsley and/or tarragon)