Support for SSO via AWS Cognito JWT Method

Might be the wrong place to make such a request, but due to lack of SAML/SSO/MFA,etc, would be ideal to be able to leverage existing authentication gateways such as Cognito. The existing SSO plugin only supports simpler HTTP header methods.

## Possible Solution
Great articles below
https://www.stackery.io/blog/authentication-aws-cognito/
https://github.com/awslabs/aws-support-tools/tree/master/Cognito/decode-verify-jwt
https://docs.aws.amazon.com/cognito/latest/developerguide/amazon-cognito-user-pools-using-tokens-with-identity-providers.html#amazon-cognito-user-pools-using-the-id-token

Feel free to discard if out of scope for this repo.