Custom domain support with Cognito

**Describe the bug**
We configured custom domain for cognito hosted UI and when user tries to login it calls both cognito domain (ending up with invalid_grant error) and to custom domain (success response) and sometimes it fails for both of them. When I run "amplify status" it gives Hosted UI endpoints with cognito domain. I tried to update the domain name using "amplify update auth" and it doesn't allow me to update custom domain name. I tried to override auth configurations in my App.js file with custom domain but somehow it still calls both cognito domain and custom domain.

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