chore(spec2cdk): ensure strings are passed to attributes

[leonmk-aws]

Issue # (if applicable)

Closes #.

Reason for this change

In some languages for which jsii cannot properly generate unions like Go, if a user passes the wrong property (i.e an ILayerRef instead of an IRoleRef), the error message will be unclear:

panic: ValidationError: Resolution error: Resolution error: Trying to resolve() a Construct at /Resources/${Token[GoAppStack.SampleFunction.LogicalID.139]}/Properties/role/node..

Description of changes

Add a check to ensure that all unions have been resolved to a string and throw an error if not, at runtime it will look like:

panic: TypeError: Property role should be one of iam.IRoleRef | string

Description of how you validated changes

Ran locally, updated snapshot tests. Unit test will be added once the relationships are enabled for lambda.

Checklist

• My code adheres to the CONTRIBUTING GUIDE and DESIGN GUIDELINES

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

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Thank you for contributing! Your pull request will be updated from main and then merged automatically (do not update manually, and be sure to allow changes to be pushed to your fork).

[mergify]

Thank you for contributing! Your pull request will be updated from main and then merged automatically (do not update manually, and be sure to allow changes to be pushed to your fork).

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