code: func New(key, email string, opts ...Option) (*API, error) {
  	if key == "" || email == "" {
  		return nil, errors.New(errEmptyCredentials)
  	}
  
  	api, err := newClient(opts...)
  	if err != nil {
  		return nil, err
  	}
  
  	api.APIKey = key
  	api.APIEmail = email
  	api.authType = AuthKeyEmail
  
  	return api, nil
  }
docs: // New creates a new Cloudflare v4 API client.