Add support for 'PreventUserExistenceErrors'

[hisham]

Cognito supports this setting (PreventUserExistenceErrors) which will prevent cognito from disclosing to the frontend whether a user exists in the userpool or not.

Does not look like amplify cli supports this setting. It can be added in the cloudformation file manually but the cli will reset it if 'amplify update auth' is run.

[LoganArnett]

Is this underway or can I open a PR for this?

[josefaidt]

Hey 👋 this can now be accomplished with the use of overrides! Using the following override we are able to enable PreventUserExistenceErrors

import { AmplifyAuthCognitoStackTemplate } from '@aws-amplify/cli-extensibility-helper'

export function override(resources: AmplifyAuthCognitoStackTemplate) {
  resources.userPoolClient.addPropertyOverride(
    'PreventUserExistenceErrors',
    'ENABLED'
  )
}

Closing issue 🙂