Harry is living happily ever after, but now comes “Harry Potter and the Cursed Child,” a play in two full-length parts (of course) that begins previews in London on Tuesday, June 7, opens July 30 and is being advertised as the official “eighth story in the Harry Potter canon.” Set 19 years after the “Deathly Hallows,” it features Harry as an overworked employee of the Ministry of Magic and focuses on his middle child, Albus Severus, and his struggle to come to terms with his family’s legacy.