plugin XEP-0176: Send ICE candidates buffer for initiator: - ICE buffer is now sent also for initiator. - If `ice_candidates_new_cb` is set in `session`, it will be used instead of using the `ice_candidates_new` signal. This is useful to handle internally the workflow, and will be used in incoming `Conferences` component. rel 445

these certificates are used for demo purpose only. Those must be the same as in
backend_e2e (they are generated there)