Alabama White BBQ Chicken Sandwich

Name: Alabama White BBQ Chicken Sandwich
Ingredients: 1 rotisserie chicken, skin removed and reserved and meat shredded; 1/2 cup mayonnaise; 2 tablespoons apple cider vinegar; 1/2 tablespoon prepared horseradish; 1/2 teaspoon Dijon mustard; 1/2 teaspoon freshly ground black pepper; Kosher salt; 1/2 small head red cabbage, cored and thinly sliced; 1/2 teaspoon celery salt; 1/2 tablespoon sugar; 1 to 2 dashes hot sauce, optional; 5 kosher dill pickle spears, thinly sliced lengthwise into ribbons, plus 1/4 cup dill pickle brine; 1 carrot, shredded on the large holes of a box grater; Softened unsalted butter, for the toast; 8 slices fresh Texas toast bread