By the time Sam Apple pulled up with his goldendoodle, Steve, to their resting place, he was tired from the long drive and already second-guessing his plan. He felt a little better when they stepped inside the Dogwood Acres Pet Retreat. The lobby, with its elegant tiled entrance, might have passed for the lobby of any small countryside hotel, at least one that strongly favored dog-themed decor. But this illusion was broken when the receptionist reviewed their reservation — which, in addition to their luxury suite, included cuddle time, group play, a nature walk and a “belly rub tuck-in.” Venues like this one, on Kent Island in Maryland’s Chesapeake Bay, didn’t exist when Apple was growing up in the 1980s. If you needed a place to board your dog back then, you went to a kennel, where your dog spent virtually the entire day in a small — and probably not very clean — cage. There were no tuck-ins, no bedtime stories, no dog-bone-shaped swimming pools. There was certainly nothing like ...