By Veronika Bondarenko P.F. Chang’s has something new for its frequent customers. One of the earliest forms of the chain restaurant subscription is Olive Garden’s “Never Ending Pasta Bowl.” Launched in 1995, the promotion gave customers the chance to pay $6.95 and eat as much pasta, salad and breadsticks as they can fit in one sitting. Over the next three decades, the promotion came, went and even morphed into a $100 pass that gave customers never-ending pasta at its restaurants for nine weeks. Over the last year, several food chains have toyed with what was once a rare model for anything but …