code: func (r *Rotation) String() string {
  	switch r.State {
  	case "", RotationStateStandby:
  		if r.LastRotated.IsZero() {
  			return "never updated"
  		}
  		return fmt.Sprintf("rotated %v", r.LastRotated.Format(teleport.HumanDateFormatSeconds))
  	case RotationStateInProgress:
  		return fmt.Sprintf("%v (mode: %v, started: %v, ending: %v)",
  			r.PhaseDescription(),
  			r.Mode,
  			r.Started.Format(teleport.HumanDateFormatSeconds),
  			r.Started.Add(r.GracePeriod.Duration()).Format(teleport.HumanDateFormatSeconds),
  		)
  	default:
  		return "unknown"
  	}
  }
docs: // String returns user friendly information about certificate authority.