Which boards of this CLASS have anything on them: the main room's and each breakout's, for the class report's "Board from this class".

{boards: [{room_name, label, is_breakout, ops}]}, main room first, then the breakouts in the order they were opened; a room whose board is empty or was never saved is left out, so the caller fetches only boards with ink.

A breakout's name resolves to its class. Who may list is decided on the CLASS room by the same rule as reading one board (_whiteboard_room), and that rule already lets whoever may read the class read each breakout's board, so the list hands out nothing a single read would refuse.