code: @SdkInternalApi
      final TypeToBuild configureMutableProperties(TypeToBuild clientInterface) {
          AmazonWebServiceClient client = (AmazonWebServiceClient) clientInterface;
          setRegion(client);
          client.makeImmutable();
          return clientInterface;
      }
docs: Region and endpoint logic is tightly coupled to the client class right now so it's easier to
  set them after client creation and let the normal logic kick in. Ideally this should resolve
  the endpoint and signer information here and just pass that information as is to the client.
  
  @param clientInterface Client to configure