Avoid rate limit errors on Cognito auth endpoints

Hi,

there are four types of resolution for this:

1. As pointed in the Issue, you should handle 4XX Rate Limit error code gracefully
2. You need to understand if the rate limiting applies to authentication or refresh of the access token. A. if Authentication, you can try to request a quota increase for Cognito , see Quotas page https://docs.aws.amazon.com/cognito/latest/developerguide/limits.html B. If refresh of the access token, you might want to increase the life time of the Access token in the User Pool, see token Expiration parameter https://docs.aws.amazon.com/cognito/latest/developerguide/user-pool-settings-client-apps.html
3. Finally if this is bad traffic DDOS you, you apply an AWS WAF WebACL to filter out traffic before reaching Cognito see https://docs.aws.amazon.com/cognito/latest/developerguide/user-pool-waf.html