[Question] Is it possible to specify a pre-existing rest-api url WITHOUT a custom domain?

I would like to use chalice to manage different api handlers for the same api gateway.
As far as i've seen, it isn't possible to specify a `rest_api_url`, only a custom domain. Is that right?

Start by reviewing Chalice's existing custom-domain configuration and how it identifies an API Gateway REST API. Determine whether a pre-existing REST API URL can be selected without a custom domain, then verify the behavior with the relevant API Gateway deployment flow; the issue names no files or tests to begin with.

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