code: func (u *User) IDForProvider(provider string) string {
  	id := u.ProviderCredentials()[provider].Get(common.CredentialsKeyID).Data()
  	switch id.(type) {
  	case string:
  		return id.(string)
  	case float64:
  		return strconv.FormatFloat(id.(float64), 'f', 0, 64)
  	}
  	return ""
  }
docs: // IDForProvider gets the ID value for the specified provider name for
  // this user from the ProviderCredentials data.