{id: Id;}
It is only allowed, if the given speaker is waiting.
If the given speaker has speech_state == "interposed_question", pause the current speaker via speaker.pause. Otherwise, stop the current speaker (if it exists) via speaker.end_speech.
Starts the speech of the given speaker: Sets begin_time to the current system time.
If meeting/list_of_speakers_couple_countdown is true, the countdown given by
meeting/list_of_speakers_countdown_id must be restarted (see
Countdowns).
If the given speaker has speech_state == "intervention", the countdown_time of the countdown has to be set to current_timestamp + meeting/list_of_speakers_intervention_time first.
If the given speaker has speech_state == "interposed_question", the countdown_time of the countdown has to be set to current_timestamp first.
If the given speaker has a structure_level_id set, the current_start_time of the structure level
has to be set to the speaker's begin_time.
The request user needs list_of_speakers.can_manage.