ot::BorderRouter::RoutingManager::GetRouteInfoOptionPreference() const method

Gets the current preference used when advertising Route Info Options (RIO) in Router Advertisement messages sent over the infrastructure link. The RIO preference is determined as follows: - If explicitly set by user by calling `SetRouteInfoOptionPreference()`, the given preference is used. - Otherwise, it is determined based on device's role: Medium preference when in router/leader role and low preference when in child role.