Migration: Codegen support for Gen2 reference auth from Gen1 import auth

[abhi7cr]

Description of changes

Add Codegen support for Gen2 reference auth from Gen1 import auth.
Note: we codegen the references to all the userpool groups by default. Users could later remove the ones they don't need to reference in other categories.

Example output:

import { referenceAuth } from "@aws-amplify/backend";
export const auth = referenceAuth({
    userPoolId: "userPoolId",
    userPoolClientId: "userPoolClientId",
    identityPoolId: "identityPoolId",
    unauthRoleArn: "unauthRoleArn",
    authRoleArn: "authRoleArn",
    groups: {
        Admin: "admin",
        ReadOnly: "readOnly"
    }
});

Description of how you validated changes

Ran codegen command, updated Gen2 backend package to a tagged release that supports refAuth and ran npx sandbox deploy.

Checklist

• PR description included
• yarn test passes
• Tests are changed or added
• Relevant documentation is changed or added (and PR referenced)
• New AWS SDK calls or CloudFormation actions have been added to relevant test and service IAM policies
• Pull request labels are added

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[awsluja]

what are we doing about the other client id?

[abhi7cr]

I think import auth in gen1 needs only 1 client (web): https://docs.amplify.aws/gen1/javascript/build-a-backend/auth/import-existing-resources/