code: func (v *VaultProvider) SetIntermediate(intermediatePEM, rootPEM string) error {
  	if v.isRoot {
  		return fmt.Errorf("cannot set an intermediate using another root in the primary datacenter")
  	}
  
  	_, err := v.client.Logical().Write(v.config.IntermediatePKIPath+"intermediate/set-signed", map[string]interface{}{
  		"certificate": fmt.Sprintf("%s\n%s", intermediatePEM, rootPEM),
  	})
  	if err != nil {
  		return err
  	}
  
  	return nil
  }
docs: // SetIntermediate writes the incoming intermediate and root certificates to the
  // intermediate backend (as a chain).