I am evaluating using Shopify for a client's commerce website. One of the requirements is that customers be able to log in to the website using the account they have created for the client's other mobile application. Customers would then be able to get product recommendations based on data available from this other application. I realize that much of this would need to be built custom, on an external stack, but for the single sign-on aspect, is this at all possible? The closest I have found is Multipass documentation, but that appears to only be available for Shopify+ which is not appropriate for my client.
Has anyone had any luck achieving this in any other way?