How to get logout url in .well-known/openid-configuration endpoint?

The Cognito Hosted UI does not currently support OIDC IdP logout. If you need to add that functionality you'll have to redirect to your application on logout using the logout_uri request parameter and have your application call the logout endpoint for the OIDC provider. https://docs.aws.amazon.com/cognito/latest/developerguide/logout-endpoint.html