Define authoritative sync master

Hi! If in Photon among all the current room players I wanted to define a single person (say, to send certain authoritative messages to others), and I don't care about who that person is except I don't want to define multiple ones and I want for every other client to reliably also know who's that authority, how would I do that? Also considering that this person may leave, so a new person would need to be dynamically chosen as fallback and switch at any time. Thanks!