Katharine McPhee and David Foster are headed to the altar. The former "American Idol" contestant and the Canadian musician confirmed their engagement on Tuesday. Foster, 68, popped the question to McPhee, 34, while the two were vacationing in Capri, Italy, according to the former "Smash" star. "He did it at the top of this mountain in Anacapri," McPhee wrote in a text exchange she shared on Instagram. "Totally dark, only stars." This will be McPhee's second marriage. Foster has been married four times and has five children. His last marriage was to "Real Housewives of Beverly Hills" star, Yolanda Hadid....