API Gateway endpoint to Cloudfront endpoint

Hello everyone!

Do you know if there is a way to change an API endpoint in `amplifyconfiguration.json` to be a _CloudFront_ endpoint?

I have a WAF connected to CloudFront endpoint. This link is associated with an API Gateway URL.

For example:
```json
"apiProject": {
"endpointType": "REST",
"endpoint": "https://xxxxxxxxx.cloudfront.net",
"region": "...",
"authorizationType": "AWS_IAM"
}
```

The error is:
> The request signature we calculated does not match the signature you provided. Check your AWS Secret Access Key and signing method. \n\nThe Canonical String for this request should have been ... host: xxxxxxxxxx.execute-api.xx-xxxxx-x.amazonaws.com

Is there a way to use a CloudFront URL in the endpoint field? Thanks.

Start by tracing how amplifyconfiguration.json endpoint values are parsed and how AWS_IAM requests are signed; reproduce the signature mismatch with the CloudFront URL and compare it with the API Gateway URL. Done means confirming whether this endpoint is supported and documenting the required configuration or recording the limitation.

Written by the indexing model from the issue text.