code: func (c *Client) RotateCertAuthority(req RotateRequest) error {
  	caType := "all"
  	if req.Type != "" {
  		caType = string(req.Type)
  	}
  	_, err := c.PostJSON(c.Endpoint("authorities", caType, "rotate"), req)
  	return trace.Wrap(err)
  }
docs: // RotateCertAuthority starts or restarts certificate authority rotation process.