Anthony Rapp put a ring on it! On Saturday, the Broadway and Star Trek: Discovery star announced his engagement to longtime boyfriend Ken Ithipholon on social media. "So something happened tonight," Rapp, 48, wrote on Instagram and Twitter with a photo of Ithiphol proudly showing off his ring. "I asked @teerakeni if he would marry me and he said yes. I am so very happy and I'm so very thrilled to share this new…