int manager_add_button(Manager *m, const char *name, Button **_button);
int manager_add_seat(Manager *m, const char *id, Seat **_seat);
int manager_add_session(Manager *m, const char *id, Session **_session);
int manager_add_button(Manager *m, const char *name, Button **_button);
int manager_add_seat(Manager *m, const char *id, Seat **_seat);
int manager_add_session(Manager *m, const char *id, Session **_session);